THE FIRST EXPERIMENTS WITH THE ELECTRIC LIGHT.

Ohms.Armature resistance 0.4 w.Field-magnet resistance 0.17 w.Insulation resistance 1,500,000 w.

This motor was only completed on the morning before reading the paper; it could not, therefore, be tested as to its various capacities.

We have next to consider the principle of applying the motive power to the propulsion of a launch. The propellers hitherto practically applied in steam navigation are the paddle-wheel and the screw. The experience of modern steam navigation points to the exclusive use and advantage of the screw propeller where great speed of shaft is obtainable, and the electric engine is pre-eminently a high-speed engine, consequently the screw appears to be most suitable to the requirements of electric boats. By simply fixing the propeller to the prolonged motor shaft, we complete the whole system, which, when correctly made, will do its duty in perfect order, with an efficiency approaching theory to a high degree.

FIG. 1.--RECKENZAUN'S ELECTRICAL HORSE POWER DIAGRAM.Draw a square, A B C D--divide B C into 746 parts, andC D into 1,000 parts, or, generally, let a division on C Dbe 0.746 of a division on B C, so that we can use thehorizontal lines cutting A B as a horse power scale.A B, in the above diagram, gives 1,000 horse power, ifthe line B C represents 746 volts, and C D 1,000 amperes.Let x = any number of volts, y the amperes,and h the horse power, thenh/x = y/100 :. h = xy/746A fine wire or thread stretched from o as a center to therequired division on C D will facilitate references.

Whatever force may be imparted to the water by a propeller, such force can be resolved into two elements, one of which is parallel, and the other in a plane at right angles to the keel. The parallel force alone has the propelling effect; the screw, therefore, should always be so constructed that its surfaces shall be chiefly employed in driving the water in a direction parallel to the keel from stem to stern.

Fig. 2--KAPP'S DIAGRAM.

It is evident that a finely pitched screw, running at a high velocity, will supply these conditions best. With that beautiful screw lying on this table, and made by Messrs. Yarrow, 95 per cent. of efficiency has been obtained when running at a speed of over 800 revolutions per minute--that is to say, only 5 per cent was lost in slip.

Reviewing the various points of advantage, it appears that electricity will, in time to come, be largely used for propelling launches, and, perhaps, something more than launches.

In conclusion, quoting Dr. Lardner's remarks on the subject of steam navigation of nearly fifty years ago, he said:

"Some, who, being conversant with the actual conditions of steam engineering as applied to navigation, and aware of various commercial conditions which must affect the problem, were enabled to estimate calmly and dispassionately the difficulties and drawbacks, as well as the disadvantages, of the undertaking, entertained doubts which clouded the brightness of their hopes, and warned the commercial world against the indulgence of too sanguine anticipation of the immediate and unqualified realization of the project. They counseled caution and reserve against an improvident investment of extensive capital in schemes which still be only regarded as experimental, and which might prove its grave. But the voice of remonstrance was drowned amid the enthusiasm excited by the promise of an immediate practical realization of a scheme so grand.

"It cannot," he continues, "be seriously imagined that any one who had been conversant with the past history of steam navigation could entertain the least doubt of the abstract practicability of a steam vessel making the voyage between Bristol and New York. A steam vessel, having as cargo a couple of hundred tons of coals, would,cæteris paribus, be as capable of crossing the Atlantic as a vessel transporting the same weight of any other cargo."

Dr. Lardner is generally credited with having asserted that a steam voyage across the Atlantic was "a physical impossibility," but in the work from which I took the liberty of copying his words he denies the charge, and says that what he did affirm was, that long sea voyages could not at that time be maintained with that regularity and certainty which are indispensable to commercial success, by any revenue which could be expected from traffic alone.

The practical results are well known to us. History repeats itself, and the next generation may put on record our week attempts, our doubts and fears of this day. Whether electricity will ever rival steam, remains yet to be proved; we may be on the threshold of great things. The premature enthusiasm has subsided, and we enter upon the road of steady progress.

Mr. Wm. H. Preece, the chairman, in inviting discussion, said that no doubt those present would like to know something about the cost of such a boat as Mr. Reckenzaun described, and he hoped that gentleman would give them some information on that point.

Admiral Selwyn thought Mr. Reckenzaun was a little below the mark when he talked about the dream of getting 5 horse power for one pound--he would not say of coal, but of fuel. For some months he had seen ½ lb. of fuel produce 1 horse power, and he knew it could be done. That fuel was condensed concentrated fuel in the shape of oil. When this could be done, electrical energy also could be obtained much cheaper, but if it were extended to yachts, he thought that would be as far as any one now present could be expected to see it go. Still he thought there was a future for it, and that future would be best advanced by considering the question on which he had touched. First, the employment of a cheaper mode of getting the power in the steam engine; and, secondly, a cheaper and higher secondary battery. In a railway train weight was a formidable affair, but in a floating vessel it was still more important. He did not think, however, that a light secondary battery was by any means an impossibility. Mr. Loftus Perkins had actually produced by improvements in the boiler and steam engine two great things: first, one indicated horse power for a pound of fuel per hour, and next he had devised a steam engine of 100 horse power, of a weight of only 84 lb. per horse power, instead of 304 lb., which was about the average. Those were two enormous steps in advance, and under a still more improved patent law he had no doubt things would be brought forward which would show a still greater progress. Within the last fifteen days, nearly 2,000 patents had been taken out, as against 5,000 in the whole of the previous year, which showed how operative a very small and illusory inducement had been to encourage invention. He had long been known as an advocate of patent law reform, and, therefore, felt bound to lose no opportunity of calling attention to its importance. Invention was in the hands of the inventor, the creator of trade. If, without robbing anybody, one wished to produce property, it must be done by improving manufactures as a consequence of inventions. In one instance alone it bad been proved that a single invention had been the means of introducing twenty millions annually, upon which income tax was paid.

Mr. Crampton said he did not think steam could ever compete with electricity, under certain circumstances; but, at the same time, it would be a long time before it was superseded. He should like very much to see the compressed oil, one-sixth of a pound of which would give 1 horse power per hour.

Admiral Selwyn said he had seen a common Cornish boiler doing it years ago.

Mr. Crampton said it had never come under his notice, and he had no hesitation in saying that no such duty ever was performed by any oil, because he never heard of any oil which evaporated more than eighteen to twenty-two pounds of water per pound. However, he was delighted to hear of such progress being made, and though he had been for so many years connected with steam, he never expected it would last forever. He was now making experiments for some large shipowners, for the purpose of facilitating feeding and doing away with dust, but let him succeed to what extent he might, steam would never compete with electricity for such small vessels as these launches.

The Chairman asked if he rightly understood Admiral Selwyn that he had recently seen an invention in which one-sixth of a pound of condensed fuel would give 1 horse power per hour.

Admiral Selwyn said it was now some years ago since he saw this going on, but the persons who did it did not know how or why it was done. He had studied the question for the last ten years, and now knew therationaleof it, and would be prepared shortly to publish it. He knew that 22 was the theoretical calorific value of the pound of oil, and never supposed that oil alone would give 46 lb., which he saw it doing. He had found out that by means of the oil forming carbon constantly in the furnace, the hydrogen of the steam was burned, and that it was a fallacy to suppose that an equal quantity of heat was used in raising steam, at a pressure of, say, 120 lb. to the square inch, as the hydrogen was capable of developing when properly burned. There were, however, conditions under which alone that combustion could take place--one being that the heat of the chamber must be 3,700°, and that carbon must be constantly formed.

Mr. Gumpel said with regard to the general application of electricity to the propulsion of vessels as well as to railway trains, he believed that many of those present would live to see electricity applied to that purpose, because there were so many minds now applied to the problem, that before long he had no doubt we should see coal burned in batteries, as it was now burned in steam boilers. The utmost they could do, then, would be about 50 per cent. less than Admiral Selwyn said could be accomplished with condensed fuel. He could not but wonder where Admiral Selwyn obtained his information, knowing that a theoretically perfect heat engine would only give 23 per cent. of the absolute heat used, and that a pound of the best coal would give but 8,000 and hydrocarbon 13,000 heat units, while hydrogen would give 34,000; and calculating it out, how was it possible to get out of one-sixth of a pound of carbon, or any hydrocarbon, the amount of power stated? No doubt, when Admiral Selwyn applied the knowledge which physicists would give him of the amount of power which could be got out of a certain amount of carbon and hydrogen, he would find that there was a mistake somewhere.

Mr. Reckenzaun, in reply, said it would be very difficult to answer the question put by the Chairman, as to the cost of an electric launch--quite as difficult as to say what would be the cost of a steam launch. It depended on the fittings, the ornamental part, the power required, and the time it was required to run. If such a launch were to run constantly, two sets of accumulators would be required, one to replace the other when discharged. This could be easily done, the floor being made to take up, and the cells could be changed in a few minutes with proper appliances. As to Admiral Selwyn's remarks about one-sixth of a pound of fuel per horse power, he had never heard of such a thing before, and should like to know more about it. Mr. Loftus Perkins' new steam engine was a wonderful example of modern engineering. A comparatively small engine, occupying no more space than that of a steam launch of considerable dimensions, developed 800 horse power indicated. From a mechanical point of view, this engine was extremely interesting; it had four cylinders, but only one crank and one connecting rod; and there were no dead centers. The mechanism was very beautiful, but would require elaborate diagrams to explain. Mr. Perkins deserved the greatest praise for it, for in it he had reduced both the weight of the engine and the consumption of fuel to a minimum. He believed he used coke and took one pound per horse power. He should not like to cross the Channel in the electric launch, if there was a heavy sea on, for shaking certainly did not increase the efficiency of the accumulators, but a fair amount of motion they could stand, and they had run on the Thames, by the side of heavy tug boats causing a considerable amount of swell, without any mishap. Of course each box was provided with a lid, and the plates were so closely packed that a fair amount of shaking would not affect them; the only danger was the spilling of the acid. Mr. Crohne had remarked that a torpedo boat of that size would have 100 indicated horse power, but then the whole boat would be filled with machinery. What might be done with electricity they had, as yet, no idea of. At present, they could only get 33,000 foot pounds from 1 lb. of lead and acid, though, theoretically, they ought to get 360,000 foot pounds. Iron in its oxidation would manifest theoretically 1,900,000 foot pounds per lb. of material. As yet they had not succeeded in making an iron accumulator; if they could, they would get about six or seven times the energy for the same weight of material, or could reduce the weight proportionately for the same power, and in that way they might eventually get 70 horse power in a boat of that size, because the weight of the motor was not great. With regard to the formation of a film on the surface, no doubt a film of sulphate of lead was formed if the battery stood idle, but it did not considerably reduce its efficiency; as soon as it was broke through by the energy being evolved from it, it would give off its maximum current. They knew by experience that, with properly constructed accumulators, 80 per cent. of the energy put into them was returned in work. It was quite certain, as Mr. Crampton said, that it would be a long time before steam was superseded: he did not prophesy at all; and he entitled his paper "Electric Launches," because it would be presumptuous to speak of anything more until larger vessels had been made and tried. With regard to Mr. Gumpel's remark on the friction of the propeller, he would say that it was constructed to run 900 revolutions; if it were driven by a steam engine, and the speed reduced to 300, not only would the pitch have to be altered, but the surface would have to be larger, which would entail more friction. Mr. Crohne would bear him out that they lost only 5 per cent. by slip and friction combined, on an average of a great number of trials, both with and against the current.

The Chairman in proposing a vote of thanks to Mr. Reckenzaun, said he rejoiced to find that that gentleman had proved, to one man at least, that his views had been mistaken. He found in these days of the practical applications of electricity, that the ideas of most practical men were gradually being proved to be mistaken, and every day new facts were being discovered, which led them to imagine that as yet they were only on the shore of an enormous ocean of knowledge. It was quite impossible to say what these electric launches would lead to. Certain points of great importance had been pointed out; they gave great room and they were always ready. For lifeboat and fire engine purposes, as Captain Shaw pointed out at Vienna, this was of great consequence.

At first they were led to believe that there was great stability, but that idea had been a little shaken, not as to the boat itself, but as to the influence of the motion of the water upon the constancy of the cells. But these boats were only intended for smooth water, and if they could not be adapted for rough water, he feared Admiral Selwyn's suggestion of the application of this principle to lifeboats would fall to the ground; but if secondary batteries were not calculated as yet to stand rough usage, it only required probably some thought on Mr. Reckenzaun's part to make them available even in a gale. Enormous strides were being made with regard to these batteries. No one present had been a greater skeptic with regard to them at first than be himself; but after constant experiments--employing them, as he had done for many months, for telegraphic purposes--he was gradually coming to view them with a much more favorable eye. The same steps which had rendered all scientific notions practicable, had gradually eliminated the faults which originally existed, and they were now becoming good, sound, available instruments. At present, he could only regard this electric launch as a luxury. He had hoped that Mr. Reckenzaun would have been able to say something which would have enabled poor men to look forward to the time when they might enjoy themselves in them on the river; but he was told at Vienna, when he enjoyed two or three trips in this boat on the Danube, that her cost would be about £800, which was a little too much for most people. They wanted something more within their reach, so that at various points on the river they might see small engines constantly at work supplying energy to secondary batteries, and so that they might start on a Friday evening, and go up as far as Oxford, or higher, and come down again on Monday morning. He must congratulate Mr. Reckenzaun on the excellent diagrams he had constructed. The trouble of calculating figures of this sort was very great when making experiments; and the use of diagrams and curves expedited the labor very much. At present they were passing through a stage of electrical depression; robbery had been committed on a large scale; the earnings of the poor had been filched out of their pockets by sanguine company promotors; an enormous amount of money had been lost, and the result had been that confidence was, to a great extent, destroyed; but those who had been wise enough to keep their money in their pockets, and to read the papers read in that room, must have seen that there was a constant steady advance in scientific knowledge of the laws of electricity and in their practical applications, and as soon as some of these rotten, mushroom companies had been wiped out of existence, they might hope that real practical progress would be made, and that the day was not far distant when the public would again acquire confidence in electrical enterprise. They would then enable inventors and practical men to carry out their experiments, and to put electrical matters on a proper footing.

Electric lighting dates back, as well known; to the celebrated experiment of Sir Humphry Davy, which took place in 1809 or 1810, but the date of which is often given as 1813. There exist however, some indications that experiments on the production of the electric spark between carbons had been performed before the above named date.

Mr. S.P. Thompson has given the following interesting details in regard to this subject: In looking over an old volume of theJournal de Paris, says he, I found under date of the 22d Ventose, year X. (March 12, 1802), the following passage, which evidently refers to an exhibition of the electric arc:

"Citizen Robertson, the inventor of the phantasmagoria (magic lantern), is at present performing some interesting experiments that must doubtless advance our knowledge concerning galvanism. He has just mounted metallic piles to the number of 2,500 zinc plates and as many of rosette copper. We shall forthwith speak of his results, as well as of a new experiment that he performed yesterday with two glowing carbons.

SIR HUMPHRY DAVY'S ELECTRIC LIGHT EXPERIMENTS IN 1813.

"The first having been placed at the base of a column of 120 zinc and silver elements, and the second communicating with the apex of the pile, they gave at the moment they were united a brilliant spark of an extreme whiteness that was seen by the entire society. Citizen Robertson will repeat this experiment on the 25th."

The date generally given for the invention of the electric light by Sir Humphry Davy is 1809, but previous mentions of his experiment are found in Cuthberson's "Electricity" (1807) and in other works. In thePhilosophical Magazine, vol. ix., p. 219, under date of Feb. 1, 1801, in a memoir by Mr. H. Moyes, of Edinburgh, relative to experiments made with the pile, we find the following passage:

"When the column in question had reached the height of its power, its sparks were seen by daylight, even when they were made to jump with a piece of carbon held in the hand."

ELECTRIC LIGHTING IN PARIS IN 1844.

In theJournal of the Royal Institution, vol. i. (1802), Davy describes (p. 106) a few experiments made with the pile, and says:

"When, instead of metals, pieces of well calcined carbon were employed, the spark was still larger and of a clear white."

On page 214 he describes and figures an apparatus for taking the galvano-electric spark into fluid and aeriform substances. This apparatus consisted of a glass tube open at the top, and having at the side a tube through which passed a wire that terminated in a carbon. Another wire, likewise terminating in carbon, traversed the bottom and was cemented in a vertical position.

But all these indications are posterior to a letter printed inNicholson's Journal, in October, 1800, p. 150, and entitled: "Additional Experiments on Galvanic Electricity in a Letter to Mr. Nicholson." The letter is dated Dowry Square, Hotwells, September 22, 1800, and is signed by Humphry Davy, who at this epoch was assistant to Dr. Beddoes at the Philosophical Institution of Bristol. It begins thus:

"Sir: The first experimenters in animal electricity remarked the property that well calcined carbon has of conducting ordinary galvanic action. I have found that this substance possesses the same properties as metallic bodies for the production of the spark, when it is used for establishing a communication between the extremities of Signor Volta's pile."

In none of these extracts, however, do we find anything that has reference to the properties of the arc as a continuous, luminous spark. It was in his subsequent researches that Davy made known its properties. It will be seen, however, that the electric light had attracted attention before its special property of continuity had been observed.

It results from these facts that Robertson's experiment was in no wise anterior to that of Davy. The inventor of the phantasmagoria did not obtain the arc, properly so called, with its characteristic continuity, but merely produced a spark between two carbons--an experiment that had already been made known by Davy in 1800. The latter had then at his disposal nothing but a relatively weak pile, and it is very natural that, under such circumstances, he produced a spark without observing its properties as a light producer.

It was only in 1808 that he was in a position to operate upon a larger scale. At this epoch a group of men who were interested in the progress of science subscribed the necessary funds for the construction of a large battery designed for the laboratory of the Royal Institution. This pile was composed of 2,000 elements mounted in two hundred porcelain troughs, one of which is still to be seen at the Royal Institution. The zinc plates of these elements were each of them 32 inches square, and formed altogether a surface of 80 square meters. It was with this powerful battery that Davy, in 1810, performed the experiment on the voltaic arc before the members of the Royal Institution.

The carbons employed were rods of charcoal, and were rapidly used up in burning in the air. So in order to give longer duration to his experiment, Davy was obliged, on repeating it, to inclose the carbons in a glass globe like that used in the apparatus called the electric egg. The accompanying figure represents the experiment made under this form in the great ampitheater of the Royal Institution at London.--La Lumiere Electrique.

All those who are acquainted with the cable-lifting branch of submarine telegraphy are well aware how important a matter it is in grappling to be certain of the instant the cable is hooked. This importance increases, of course, with the age and consequent weakness of the material, as the injury caused by dragging a cable along the bottom is obviously very great.

ELECTRICAL GRAPNEL FOR SUBMARINE CABLES AND TORPEDO LINES.

It is easy also to understand the fact that in nearly all cases the most delicate dynamometers must fail to indicate immediately the presence of the cable on the grapnel, more especially in those cases where a considerable amount of slack grapnel rope is paid out. In many cases, therefore, the grapnel will travel through a cable without the slightest indication (or at least reliable indication) occurring on the dynamometer, and perhaps several miles beyond the line of cable will be dragged over, either fruitlessly, or to the peril of neighboring cables; whereas, should the engineer be advised of the cable's presence on the grapnel, the break will probably be avoided and the cable lifted; at any rate, the position of the cable will be an assured thing.

My own knowledge of cable grappling has convinced me of these facts; and I am well assured that those engineers at least who have been engaged in grappling for cables in great depths, or for weak cables in shallow water, will heartily agree with me.

In addition to the foregoing remarks re the insufficiency of the dynamometer as an instrument for indicating the presence of a cable on the grapnel, I might remind engineers of the troubles and perplexities which occur incessantly in dragging over a rocky bottom. The grapnel hooks a rock, a large increase of strain is indicated on the dynamometer, and it becomes doubtful whether the cable as well is hooked or not. Again, it frequently happens in grappling over a rocky bottom that one or more prongs are broken off, the grapnel thus becoming useless, great waste of time being thus occasioned. Fully realizing all the difficulties herein enumerated, it occurred to me that a grapnel might be constructed in such a manner as to automatically signal by electrical means the hooking of the cable, while it would ignore all strain that external causes might bring to bear on it, and thereby obviate the uncertainties attached to the use of the grapnels at present in vogue. To effect this, I designed early in 1881 a grapnel fitted in each prong with an insulated conducting surface, and a plunger and pin so arranged that the cable, when hooked, should, by the pressure that it would bring to bear on any of the plungers, cause the pin to come in contact with the conducting surface, itself in electrical communication with any suitable current detecter and battery on board the repairing ship, and thereby complete the circuit. This grapnel was successfully used on the Anglo-American Telegraph Company's repairing steamer Minia in the summer of 1881.

Subsequently, in discussing the construction of the grapnel with Captain Troot, we concluded that something was yet wanted to render the successful working in deep water absolutely sure, and we decided, consequently, to make certain alterations.

This improved form may be constructed, either with a contact-plate in each prong, or with one contact-plate common to all the prongs; the latter is somewhat simpler, and is therefore the plan that we usually adopt. Both forms are shown in the accompanying diagrams. The form of grapnel in Diagram No. 1 has one advantage over the other in this respect, viz., that should a prong be ruptured so as to render it useless, the fact would immediately be known on board. A circuit formed in such a manner, by the breaking off of a branch lead, would have greater resistance than that formed by the contact resulting from pressure of cable on the plungers; this difference would be manifested on the indicator (of low resistance) placed in circuit with the alarm-bell, or, if any doubt remained, a Wheatstone's bridge, or simpler still, a telephone might be made use of.

In some cases we may protect the plungers from the pressure of ooze, etc., by guards fitted to the stem of the grapnel, but in practice we have not found these to be necessary.

The water is allowed free access around and about each separate part, in order that its pressure shall be equal on all sides. This arrangement renders the grapnel as effectual in the deepest as in the shallowest water.

By making the plungers in two pieces, with a rubber washer or its equivalent between them, we prevent mud or ooze from getting behind and interfering with their working. As the hole in the rubber surrounding the contact-plate, by caused the passage of the pin through it, closes up as soon as the pressure is removed, leaving in the rubber a fault of exceedingly high resistance, the rubber does not require renewing.

In the rubber in which we embedded the contact-plate, we place a layer or more of tinfoil or other easily pierced conducting surface, through which the pin passes on its way to the contact-plate proper. This method we have adopted in order to make the assurance of contact doubly sure.

The grapnel just described we had in use on the Minia since April last. We have tried it severely, and have never known it to fail. No swivel has been used with the rope, in the heart of which is the insulated wire, as it would allow the grapnel to turn over on the bottom, and would be apt to twist and break the wire short off. As a matter of fact, the grapnel will turn, and does turn, with the rope; a swivel is therefore of no value. We are perfectly awake, however, to the fact that a grappling-rope should be made in a manner that will not allow it to kink; and engineers should avail themselves of such rope, especially in deep water. Patents have lately been granted to Messrs. Trott & Hamilton for the invention of a form of rope or cable answering all the requirements of this work.

A small type of grapnel fitted in the manner I have described may be very advantageously used for searching purposes, to ascertain the position either of telegraph or torpedo lines; by towing at a quick rate much time may be saved. The position being ascertained, if it be not desired to lift the cable, the grapnel can be released and hove on board by a tripping line, which can always be attached when such work is contemplated. The great importance of being able to localize an enemy's torpedo lines without raising an alarm will be readily seen by engineers engaged in torpedo work.

a, stem of the grapnel containing core; b, flukes; c, recess for insulated contact-plate connected to core; d, covering plate screwed on bottom of grapnel; e, button of plug; f, rubber washer and button; g, metal-plate; h, stem of plug, on which in the under counter-sink, U is a small metal disk which prevents the fittings from fallings out; i, needle; j, spring; k, counter-sink for head of plug; l, counter-sink for spring.

A new magnetic balance has been described before the Royal Society by Prof. D. E. Hughes, F.R.S., which he has devised in the course of carrying out his researches on the differences between different kinds of iron and steel. The instrument is thus described in theProceedings of the Royal Society:

"It consists of a delicate silk-fiber-suspended magnetic needle, 5 cm. in length, its pointer resting near an index having a single fine black line or mark for its zero, the movement of the needle on the other side of zero being limited to 5 mm. by means of two ivory stops or projections.

When the north end of the needle and its index zero are north, the needle rests at its index zero, but the slightest external influence, such as a piece of iron 1 mm. in diameter 10 cm. distant, deflects the needle to the right or left according to the polarity of its magnetism, and with a force proportional to its power. If we place on the opposite side of the needle at the same distance a wire possessing similar polarity and force, the two are equal, and the needle returns to zero; and if we know the magnetic value required to produce a balance, we know the value of both. In order to balance any wire or piece of iron placed in a position east and west, a magnetic compensator is used, consisting of a powerful bar magnet free to revolve upon a central pivot placed at a distance of 30 or more cm., so as to be able to obtain delicate observations. This turns upon an index, the degrees of which are marked for equal degrees of magnetic action upon the needle. A coil of insulated wire, through which a feeble electric current is passing, magnetizes the piece of iron under observation, but, as the coil itself would act upon the needle, this is balanced by an equal and opposing coil on the opposite side, and we are thus enabled to observe the magnetism due to the iron alone. A reversing key, resistance coils, and a Daniell cell are required."

The general design of the instrument, as shown in a somewhat crude form when first exhibited, is given in the figure, where A is the magnetizing coil within which the sample of iron or steel wire to be tested is placed, B the suspended needle, C the compensating coil, and M the magnet used as a compensator, having a scale beneath it divided into quarter degrees.

The idea of employing a magnet as compensator in a magnetic balance is not new, this disposition having been used by Prof. Von Feilitzsch in 1856 in his researches on the magnetizing influence of the current. In Von Feilitzsch's balance, however, the compensating magnet was placed end on to the needle, and its directive action was diminished at will, not by turning it round on its center, but by shifting it to a greater distance along a linear scale below it. The form now given by Hughes to the balance is one of so great compactness and convenience that it will probably prove a most acceptable addition to the resources of the physical laboratory.--Nature.

Cast iron may be hardened as follows: Heat the iron to a cherry red, then sprinkle on it cyanide of potassium and heat to a little above red, then dip. The end of a rod that had been treated in this way could not be cut with a file. Upon breaking off a piece about one-half an inch long, it was found that the hardening had penetrated to the interior, upon which the file made no more impression than upon the surface. The same salt may be used to caseharden wrought iron.

The accompanying engraving shows a form of Thomson's double bridge, as modified by Kirchhoff and Hausemann. The chief advantage claimed for this instrument consists in the fact that all resistances of defective contact between the piece to be measured and the battery are entirely eliminated--an object of prime importance in measuring very small resistances. By the use of this instrument resistances can be measured accurately down to one-millionth of a Siemens unit.

The general arrangement of the instrument is shown in Fig. 1; Fig. 2 being a diagram of the electrical connections.

FIG. 1.--KIRCHHOFF AND HANSEMANN'S BRIDGE FORMEASURING SMALL RESISTANCES.

The piece of metal to be measured, M, is placed in the measuring forks, gg, in such a manner that the movable fork is removed as far as possible from the stationary one; if the weight of the piece be insufficient to secure a good connection, additional weights may be placed upon it. The main circuit includes the battery, B (Fig. 2), consisting of from two to four Bunsen cells, the key, T, the German silver measuring wire, N, and the piece of metal resting on the forks, all being joined in series. The German silver wire, N, is traversed by two movable knife-edge contacts, cc, as shown. Connections are made between these contacts, cc, the resistance box, the prongs, k and l, of the forks, gg, and the reflecting galvanometer, as shown in Fig. 2. A resistance of ten units is inserted at o and n, while at m and p twenty units or one thousand units are inserted. The positions of cc are then varied until the galvanometer shows no deflection when the key, T, is depressed.

FIG. 2.--DIAGRAM SHOWING ELECTTRICAL CONNECTIONS OF BRIDGE.

When such is the case, the ratio of resistances n/m is equal to o/p; letting M equal the resistance of the metal bar between the points, h and i, and N equal to the resistance between the points, cc, on the measuring wire, N, then we shall have

M = N (n/m) = N (o/p).

Knowing the cross section in millimeters, Q, of the bar, and observing the temperature, t, in degrees Centigrade, its conductivity, x, as compared with mercury can be determined. If L be the distance, h l or k i, in meters, then

x = (1/m) (L/Q) (1 + at).

For pure metals the value of a may be taken at 0.004; but alloys have a different coefficient. The instrument is made by Siemens and Halske, and is accompanied by a table giving resistances per millimeter of the measuring wire, N.--Zeitsch. für Elektrotechnik.

[Footnote: For a full account of experiments relating to magnetism on railways in New York city, see SCIENTIFIC AMERICAN, January 19,1884.]

To the Editor of the Scientific American:

An item has appeared recently in several papers, stating that New York is a highly magnetized city--that the elevated railroad, Brooklyn Bridge cables, etc., are all highly magnetized. As this might convey to the general reader the impression that the magnetism thus exhibited was peculiar to New York city, and as many of your subscribers look anxiously for your answers to numerous questions put for the elucidation of apparent, scientific mysteries, I have thought that perhaps a statement in plain language of experiments made at various times, to elucidate this subject, might, in conjunction with a diagram, serve to explain even to those who have not made a special study of science a few of the interesting phenomena connected with

Some of the first experiments I made, while professor at the Indiana State University, were detailed in the March and August numbers, 1872, of theJournalof the Franklin Institute, and I think showed conclusively that the earth, by induction, renders all articles of iron, steel, or tinned iron magnetic; possessing for the time being polarity, after they have been in a settled position for a short time.

In Dr. I. C. Draper's "Year Book of Nature" for 1873, mention is made of the experiments in which I found every rail of a N. and S. railroad exhibiting polarity.

The same statements were repeated in one of a series of articles sent by me to theIndianapolis Daily Journal, dated Jan. 20, 1877, in which I used the following language:

"Every article of iron or steel or tinned iron, by the earth's induction, becomes magnetic. Thus, if we examine our stoves, or a doorlock, or long vertical hinge, or even a high tin cup, by holding a delicate magnetic needle in the hand near those objects, we find the earth has, by induction, attracted to the lower end of the stove utensils, etc., the opposite magnetism from its own; and repelled to the upper end of the stove, etc., the same magnetism which exists in our northern hemisphere. Consequently, the bottom of the stove, or of the hinge, cup, etc., will attract the south (or unmarked end) of our needle; while the top of the stove, etc., attracts the north, or marked end of our magnetic needle. If we apply our needle to the T rails of a N. and S. railroad, we not only find that the lower flange of the rail attracts the S. end of our needle, while the upper flange attracts the N. end of our needle, but we also find, where the two rails come nearly together (say within two inches), that the N. end of the rail attracts the S. end of our needle, while the S. end of the rail attracts the N. (or marked) end of our magnetic needle."

MAGNETISM ON RAILWAYS.

Quite recently, being anxious to see the effect produced on the needle by rails laid E. and W., I experimented on some recently laid here; starting from a S. terminus, in the town of New Harmony, and gradually curving northeast, until the road pursues a due east course to Evansville. There is, however, a branch road of about half a mile, which starts from the Wabash River, at awestterminus, and runs due east to join the other, near where that main track commences its northeast curve. The results (more readily understood by an inspection of the diagram) were as follows:

1. At the south terminus of the railroad, the rails on the east side of the track as well as those on the west side attracted at their south ends the marked end of a small magnetic needle, both at the upper and lower flange; the usual vertical induction being in this case overcome by the greater lateral induction. Whenever, on progressing north, the rails were at least about two inches apart, the upper flange of the north end of any rail would attract the unmarked, while the south end of its neighbor or any other of the north and south laid rails would attract the marked end.

2. The same results were obtained from rails laid all around the northeast curve, and even after they had acquired a due west to east course; showing that each rail acquired the same magnetic polarity which would be exhibited by any magnetic needle oscillating freely in our northern hemisphere, dipping also at its north end considerably downward if suspended at its center of gravity.

3. Applying the needle at thewestterminus, a few anomalies were observed; but, especially nearer the junction, the rails all gave the normal result found on the main track.

4. The wheels of the cars standing on the north and south track followed the same law, exhibiting both vertical and lateral induction, so that the lower rims and the forward or north part of the periphery attracted the unmarked end of the needle, while the upper and rear, or south portions of the periphery of the wheel attracted the marked end.

5. The wheels of cars standing on the east and west road exhibited the following modification. The lowest rim of all the wheels, whether standing on thenorthrails or on thesouthrails of said track, in consequence of vertical induction attracted the unmarked end of the needle, and the upper rims attracted the marked end of the needle; but the middle portions of the periphery, both anterior and posterior, of the wheels standing on the north rail, attracted the unmarked end, while similar middle portions of wheels standing on south rails attracted the marked end; in consequence of horizontal induction, the wheels being connected by iron axles, and thus presenting considerable extensionacrossthe track, viz., from south to north.

Magnetite seems to have acquired its polarity in the same manner, namely by the earth's induction, when the ore contains a large enough percentage of pure iron. A large specimen (6 in. long by 3½ deep and weighing 5½ lb.) which I obtained from near Pilot Knob, Missouri, exhibits polarity, not only at its lateral ends, but also vertically, as the lower surface attracts the unmarked end of a needle, while the plane, which evidently occupied the upper surface in its native bed, attracts the marked end of the needle.

Iron fences invariably exhibit only the polarity by vertical induction; so also small buckets, bells, etc. But in the case of a bell about 3 ft. in diameter at its base, and over two feet deep, tapering to about a foot in diameter at the top, I found that although the top attracted the marked end of the needle, the bottom attracted the unmarked end of the needle only around the northerly half of the circumference, while the southern portion of this lower rim attracted the marked end in consequence of lateral induction, as in N. and S. rails.

Thus, upon a comparison of all these facts, it would appear that, if the magnetism induced by the earth is due to so-called currents of electricity, those currents must beunderneaththe rails, and must move from west to east, under the south to north rails, and from south to north under the west to east laid rails, as indicated by the arrows in the diagram.

This accords perfectly with what we should theoretically expect, in our northern hemisphere, if the electricity in the earth's crust is due to thermo-electrical currents from east to west, namely, from the more heated to the less heated portion, on any given latitude, while the earth revolves from west to east; as well as also from electrical currents trending from tropical to Arctic regions.

As the network of iron rails spreads from year to year more extensively over our continent, it will be interesting to observe whether or not any effect is produced, meteorological, agricultural, etc., by this diffusion of magnetism.

It may further interest some of your readers to have attention called to facts indicating

The year recently closed furnishes interesting corroborative testimony of an apparent law regarding the propagation of earthquake movementsmost readilyalong great circles of our globe, as well as evidence that these seismic movements are frequently transmitted along belts (approximating to great circles) coincident sometimes with continental trends, at other times with fissures which emanate in radii at every 30°, around the pole of the land hemisphere in Switzerland, as described in one of my papers, read at the Montreal meeting of the A.A.A.S.

The terms synchronism or synchronous, as here used, are not designed to imply absolute simultaneity (although that is sometimes the case with disturbances 180° apart), but are rather intended to indicate the tendency presented by these phenomena to exhibit this internal activity, during successive days, weeks, or even months, along a given great circle of the earth, especially one or more of those connected with the land center; perhaps most of all along the great circle which forms the prime vertical, when the center of land is placed at the zenith.

In order to test the above, let us examine the record of the most prominent earthquakes or volcanic eruptions for the year 1883.

Late in Dec., 1882, and early in Feb., 1883, shocks occurred in New Hampshire; on Jan. 11, 1883, also at Cairo, Illinois, and about the same time at Paducah, Ky.; Feb. 27 at Norwich, Conn., and early in Feb. at Murcia, Spain.

These, by examination of any good globe, will be found on a belt forming one and the same great circle of the earth.

Late in March and during part of April the volcano of Ometeke in Lake Nicaragua was active (after being long dormant); Panama, portions of the U.S. of Colombia, and of Chili; also, in May, Helena, M.T.; and, in June, Quito (with Cotopaxi active) were all more or less shaken by earthquakes; and are all found on one belt of a great circle.

The principal record for the remainder of the year comprised:

An earthquake at Tabreez in North Persia, early in May, 1883.

The awful destruction in Ischia, July 29 (with Vesuvius active).

The fearful eruption in the Straits of Sunda, 25th Aug. and later.

Shocks in Sumatra and at Guayaquil, about same date or early in Sept.

Shocks at Dusseldorf, according to a Berlin paper of 5th Sept.

Shocks at Santa Barbara and Los Angeles, early in Sept.

Shocks at Gibraltar and Anatolia in October.

Shocks at Malta, Trieste, and Asia Minor in October.

Azram shaken late in Sept., and great destruction between Scios and Smyrna.

Lastly, the formation of a new island in the Aleutian Archipelago. Date of outburst, early in October, 1883.

Besides these, there were several other less severe disturbances, the records of which are chiefly obtained from Nature, and which will-be referred to below.

If the globe be so placed as to have the land center at the zenith, the exact position of the new island, near Unnok, will be found under the brazen meridian, while Agram, Tabreez, Sunda, Sumatra, Quito, and Guayaquil are all on the prime vertical.

Vesuvius and Hecla were both active early in the year, and they, with the ever restless Stromboli, are situated on the great circle which forms with the land center at Mount Rosa, the radius running S. 30° E., and which would embrace the chief disturbances up to the middle of the year, including as we go north Malta, Sicily, Rome, region of the Po, Bologna, and in the Western Continent, after passing Hecla, Helena in Montana Territory, reaching in Washington Territory and Oregon the belt of it. American volcanoes: Mounts Baker, Rainier, St. Helens, Hood, and Shasta.

Still another seismic belt, starting from the ever active Fogo, and passing through Teneriffe (at that time erupted), would include the regions disturbed in Oct. and Nov., namely, Cadiz, Gibraltar, Malaga (Murcia and Valencia somewhat earlier); it then traversed the center of land, caused the earthquakes at Olmutz in Moravia, and even tremors felt at Irkutsk, as the seismic war moved along said great circle to the volcanic region of S. Japan.

Again, the belt which covers the meridian of land center (about 8°-10° E. long) covers also the region of a disturbanced area in Norway, as well as that portion of Algeria, viz., Bona, in which a mountain 800 meters high, Naiba, is gradually sinking out of sight. About 100 geo. miles E. of Bona is where Graham's Island appeared in the Mediterranean, and a few months later disappeared in deep water.

Another highly seismic belt extends from the volcanoes of Bourbon, N. Madagascar, and Abyssinia to Santoria and the oft disturbed Scios, Smyrna, and Anatolia region; and along the same great circle were shaken Patra in Greece on the 14th Nov., and Bosnia on the 15th; while shocks had been felt at Trieste and Mülhouse about the 11th, and at Styria on the 7th, and disturbances at Dusseldorf in Sept. Finally, on the 28th Dec. S. Hungary (near the confluence of the Drave with the Danube) was visited by seismic movements along this same great circle, which passes through the extinct volcanic region of the Eifel, the oft shaken Comrie in Perthshire, Scotland, the volcanic Iceland, our National Park with its thousands of geysers, the cataclysmic region of Salt Lake and the Wahsatch Mountains (so graphically described by the geologists of the U.S. Geol. Survey), giving rise in Sept. to the earthquakes of Los Angeles and Santa Barbara, and finally reaching the volcanic islands of the Marquesas group.

Thus the seismic efforts of 1883 may be seen to have expended their force partly along the great backbone of the S. and N. American Cordillera, but more especially from the center of land E. and W. along its prime vertical from Sunda to Quito, also southwesterly by the E. coast of Spain, as well as due S. through Algeria, and S. 30° E. through Rome, Naples, Sicily, etc. Finally, the autumnal catastrophes at and near Scios, Anatolia, etc., seem to have been caused by a seismic wave, propagated along the great circle, which often agitates Janina, and produces earthquakes at Agram, where this great circle crosses the prime vertical.

RICHARD OWEN.

New Harmony, Ind., 27 Feb., 1884.

Up to the present time, the methods employed in the province of Minas Geraes (Brazil) for obtaining iron permit of manufacturing it direct from the ore without the intervening process of casting. These methods are two in number:

1. Themethod by cadinhes(crucibles), which is the simpler and requires but little manipulation, but permits of the production of but a small quantity of metal at a time.

2. TheItalian method, a variation of the Catalan, which requires more skill on the part of the workmen and yields more iron than the preceding.

As these methods seem to me of interest, from the standpoint of their simplicity and easy installation, I propose to describe them briefly, in order to give as faithful and general anaperçuas possible of their application. At present I shall deal with the first one only, the one called the method byCadinhes.

The province of Minas Geraes ocupies a vast extent in the empire of Brazil, its superficies being about 900,000 square kilometers, representing nearly a third of the total surface.

The population is relatively small and is disseminated throughout a much broken country, where the means of communication are very few. So it is necessary to succeed in producing what iron is needed by means that are simple and that require but quickly erected works built of such material as may be at hand. The iron ore is found in very great abundance in this region and is very easily mined.

In the center of a mass of quartzites that seem lo constitute the upper level of the eruptive grounds of the province, there are found strata of an ore of iron designated asitabirite--a mixture of oxide of iron and quartz. These strata are of great thickness, and have numerous outcrops that permit of their being worked by quarrying.

These itabirites present themselves under two very distinct aspects and offer a certain difference in their composition. Some are essentially friable, and are called by the vulgar name ofjacutingaes. It is this variety (which is the one most easily mined) that is principally consumed in the forges. The others, on the contrary, are compact. Their exploitation is more difficult, and before putting them into the furnaces it is necessary to submit them to breakage and screening; so the use of them is more limited.

The first variety contains less iron and more gangue, but,per contra, possesses much oxide of manganese. The second, on the contrary, is formed almost wholly of oxide of iron with but little gangue and only traces of oxide of manganese. The following are analyses of these two varieties of ore:

Situation of the Forges.--A forge is usually placed on the bank of a brook, or rather of a torrent, which supplies the fall of water necessary for the motive power by means of a flume about a hundred meters in length. In most cases the forge is surrounded on all sides with a forest which yields the wood necessary for the manufacture of the charcoal, and is in the vicinity of the iron quarry, so as to reduce the expense of hauling the ore as much as possible. The neighboring rocks furnish the foundation stones and stones for the furnaces; the decomposed schist gives the cement and refractory coating, and the forest provides the wood necessary for the construction of the road, sheds, etc. The head of the trip hammer, the anvils, and the tools are the only objects that it is necessary to procure, and even these the master of the forge often manufactures in part, after beginning production with an incomplete set.

[Illustration: 7a FIG 1.--FOUR-CRUCIBLE FURNACE AND FORGE; (PLAN).]

General Arrangement of a Forge.--A forge usually consists of one or two furnaces of three or four crucibles (the one shown in plan in Fig. 1 has only one four crucible furnace, A); 1 or 2 two fire reheating furnaces, B; 1 trip hammer, C, actuated by a hydraulic wheel, D; 2 tromps which drive the wind, one of them, E, into the cadinhes (crucibles), and the other, F, into the reheating furnace; 2 anvils, G and H, placed near the furnace, for working delicate pieces; and finally, the different tools that serve for maneuvering the bloom and finishing the bars. The charcoal is preserved from rain under a shed, l. The ore, which is brought in as needed, is dumped in a pile at M, in the vicinity of the crucibles. The buildings are set back against the mountain, and the water is led in by a double flume, L and N, made of planks, and empties on one side into the wheel and into the tromp, F, and on the other into the tromp, E, and then runs into a double waste channel, P and Q, which carries it to the stream.

FIG 2.--FOUR-CRUCIBLE FURNACE; (PLAN).

Four Crucible Furnace(Fig. 2).--The arrangement of a furnace is very simple. It consists of a cube of masonry containing several cylindrical apertures with elliptic bases, whose large axis is paralleled with the smaller side of the masonry. This form recalls that of a crucible; and these cavities are, moreover, so named. In the front part of each cadinhe there is a rectangular aperture that gives access to the bottom of the crucible and facilitates the removal of the bloom therefrom. At the back part there is a small aperture for the introduction of the tuyere, and which permits, besides, of the nozzle of the latter being easily got at so as to see whether the blast is working properly.

The sides of the crucibles are covered with a thin layer of refractory clay, and their bottoms have a spherical concavity to hold the bloom. The tuyere, which is fitted to a wooden conduit of square section that runs along the back of the masonry, is placed in the axis of the cadinhes and enters the masonry at a few centimeters from the bottom in such away that its nozzle comes just flush with the surface of the refractory lining. This arrangement prevents the tuyere from getting befouled by scoriæ during the operation of the furnace and thus interfering with the wind.

Tromp.--The tromp which furnishes the necessary wind to the cadinhes consists of a hollow wooden conduit, a (Fig. 3), of square section, which enters a chamber, b, along a length of 0.1 m. This conduit, which is about 7 meters in height, receives the water from the flume through the intermedium of an ajutage of pyramidal form, which serves to choke the vein of liquid, and the extremity of which is at a few centimeters from the conduit in order to facilitate the entrance of the air; the latter being attracted by an ill defined action that is supposed to be due to its being carried along by the water, and to a depression produced by choking the flow of the liquid.

FIG. 3.--THE TROMP.

Since the air that is sucked in during the operation has constantly same pressure, there is no valve for regulating the entrance of the water into the vertical conduit. Upon issuing from the latter, the mixture of air and water strikes the surface of the water in the chamber, b, and the violence of the shock upon the bottom is deadened by the interposition of a stone. While the water is escaping through a lateral aperture in the chamber, b, the air is reaching the tuyeres through a wooden conduit of square section which is fitted to an aperture in the upper part of the chamber. This sorry arrangement, which obliges the mixture of air and water to penetrate the water at the bottom of the upright conduit, a, retards the separation of the two fluids, and results in damp air being forced into the crucibles.

The Trip Hammer.--Fig. 4 shows the general arrangement of the apparatus that go to make up the forging mill. The hammer and cam shaft have their axes parallel, and the latter is placed in the prolongation of the axis of the wheel. The hammer consists of a roughly squared beam, 4 meters in length, and of 0.25 m. section. The head, A, consists of a mass of iron weighing 150 kilos, including the weight of the straps that surround the beam on every side of the piece of iron. The axis of rotation is situated at the other extremity of the beam, B. The cam shaft which serves to maneuver the trip hammer is provided with four cams which lift the beam at a point near the hammer. The length of this shaft (to the extremity of which is adapted the water wheel) is 4.75 m., and its diameter is 0.50 m. The wheel is anovershotone, 3.25 m. in diameter by 1 m. in width. The water, which is led to it by a flume, acts upon it by its weight and impact, and is retained in the buckets and kept from overshooting the mark by a jacket made of planks.

FIG. 4.--THE TRIP HAMMER.

The anvil upon which the hammer strikes is surrounded by a bed of stones (quartzites) derived from the neighboring rocks. It is a mass of iron, 75 kilogrammes in weight. In order to prevent vibrations in the trip hammer when it is lifted, and increase the number of blows, there is established a spring beam, which is formed of unsquared timber, which is firmly fastened at one of its extremities, and which receives at the other end the shock of the hammer head when the latter reaches the end of its upward travel.

Reheating Furnace.--This is a double fire furnace, like those used in our smithies, except that the wind, instead of being forced into it by means of a bellows, is supplied by a tromp which receives water from the same channel as the wheel. The two furnace tuyeres are arranged exactly like those of the cadinhes, upon a wooden conduit which starts from the wind chamber (Fig. 5). This furnace serves to prevent the cooling of such blooms as are awaiting their turn to be shingled, and of such bars of finished iron as are being made into tools.

A forge like the one whose plan we give, may be run with 1 workman at the cadinhes, 1 assistant, 1 workman at the hammer; total, 3 men.

Furnace.--The work lasts about twelve hours per day, and three operations of three to four hours are performed in each cadinhe, thus making twelve per day. At each operation, 22.5 kilos. of ore and 45 of charcoal are used. From this there is obtained a bloom of 15 kilos. The operation is performed as follows:

While the assistant has gone to put the bloom of the preceding operation under the hammer, the workman prepares at the bottom of the crucible a bed consisting of a mixture of sand and very fine charcoal, and then fills the crucible up to its edge with charcoal. At the end of a quarter of an hour, the fuel being thoroughly aglow, the workman puts in the first charge of ore in powder (jacutingue), about 2 kilos, and covers it with charcoal.

Starting from this moment, he goes on charging every five or ten minutes with 1.5 to 2 kilos of ore, taking care in doing so to keep the crucible stuffed with charcoal, which the assistant places in piles around each cadinhe. This lasts about two and one-half hours. At the end of this time he stops putting in charcoal, and standing upon the masonry, walks from one cadinhe to another, carrying a large rod, in order to study the lay of the bloom. Then, the fire being entirely out, he scrapes out the bed of sand and charcoal that closes the opening in the bottom of the crucible, removes the mass of ferruginous scoriæ which forms a hard paste and surrounds the bloom, and takes this latter out by means of a hook.

The workman runs the four cadinhes at once, this being easily enough done, since he has neither to bother himself with regulating the wind, which enters always with the same pressure, nor with the flow of the scoriæ, which remain always at the bottom of the crucible. His role consists simply in keeping his fires running properly, being guided in this by the color of the flame without making an examination in the interior. He draws each of the four blooms out from its bed at the end of the operation, while the assistant carries the first to the hammer and the three others to the reheating furnace. He afterward cleans out the crucible, prepares the bed of sand and charcoal, fills with charcoal, and then passes to the next, and so on.

FIG. 5.--REHEATING FURNACE.

Trip Hammer.--The workman at the hammer takes the bloom from the hands of the assistant and shingles it under the head. Then he begins to give it shape, bringing it to the state shown at c, in Fig. 7. The assistant then brings him another bloom and takes the one that has been shingled to the reheating furnace, where he heats but one of its extremities. When the four blooms have been shingled, the workman takes up the first and begins to draw out one of its extremities, which he afterward cools in water and uses as a handle for finishing the work, d. Then he reheats the other extremity, and, after drawing it out as he did the other, obtains a bar of finished iron which he doubles, as shown at e, to thus deliver to the trade.

FIG. 6.--CADINHE IN OPERATION.

One of these bars weighs from 11 to 12 kilogrammes. It will be seen that, during the course of the work, the furnace workmen and the hammer workmen have well defined duties to perform; but it is not the same with the assistant, who goes from one to the other according to requirements. There are, however, some forges in which each of the workmen has an assistant, since the blooms produced are heavier, and one assistant would not suffice for the work of the two men. In such a case the assistant at the crucibles carries the blooms to the reheating furnace, and the assistant at the hammer carries them from thence to the hammer.

FIG. 7.--WORKING THE BLOOM.

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