Fig 10, De Dion and Bouton Traction engine and omnibusFig.10.
The Count de Dion was one of the most enthusiastic organizers of the Paris to Bordeaux competition in 1895, and naturally his firm took part in the trials. They entered three vehicles for competition; one of these, called No. 1, was the traction engine which had taken part in the 1894 trials, and which we have already described. For the second time this machine gave very excellent results, as it made the distance from Paris to Angoulème (280 miles) in 30 hours, but on account of various mishaps it had to run very slowly from Angoulème to Bordeaux (84 miles), taking, in fact, 31 hours for this part of the journey, and not arriving until long after it had been ruled out of the competition.
Their second vehicle, No. 2, was a four seated brake which was, in fact, a modified traction engine. The boiler, which was of the De Dion and Bouton type, had a heating surface of 36 square feet, and was registered at 200 lb. per square inch; it weighed 550 lb. As to the motor, it was a Woolfe engine, the moving parts of which were carefully counterbalanced. The cranks were set at an angle of 180°; the diameter of the high pressure cylinder was 2.95 in., and that of the low pressure 5.90 in.; the low pressure cylinder was steam jacketed. This motor, which weighed 330 lb., developed 11 horse power at a speed of 800 revolutions. The engine was coupled direct to the shaft of the differential motion, on which were mounted two pinions for changing the speed, and which could be moved to and fro on the shaft; the movement of the differential gear was transmitted to the wheels by articulated shafts, such as those we have already referred to in describing the traction engine; sufficient water and coke could be carried for a run of 45 miles, and on a good road a speed of more than 25 miles an hour was obtained.
Fig 11. De Dion and Bouton Traction engine and omnibusFig.11.
Messrs. De Dion and Bouton anticipated great things from this carriage, and for the long run from Paris to Bordeaux they had provided only three changes of drivers, in order that the machine might be in as few hands as possible. Their hopes, however, were not realized, for although it made a better start than any of the other competitors, it only succeeded in running for 125 miles; after having passed Blois the transmission shaft broke, and the brake was useless for the time being, but the machine did enough to satisfy the constructors of the soundness of their idea; it ran the 34.5 miles between Versailles and Etampes in 2 hours and 16 minutes, making an average speed of 15 miles an hour over difficult country; between Versailles and Blois the speed touched nearly 18 miles.
The vehicle No. 3 was a tricycle driven by a petroleum motor; this was not seriously entered for competition, but rather to show a first effort of a new departure which the constructors have since followed with some success. At the present time Messrs. De Dion and Bouton are making preparations to take part in thecompetition which is to be arranged for the autumn of the present year. They have a traction engine with considerable modifications in its design, with which they, expect to run from Paris and Marseilles, and they have the intention of hauling with it one of the 40-seat omnibuses of the Paris Company, which is usually drawn by three horses. Fig. 10 is a general view of the engine attached to the omnibus. This type of vehicle is furnished with a compound engine, which can be worked up to 30 horse power, and which is to be capable of hauling a load of 5 tons at a speed of 12.5 miles; the principal points of difference between this machine and the other, which we have already described, lie in the great care which has been bestowed on the details, the precautions taken to secure the moving parts from dust, and the oil bath in which the engine works. The water supply carried is sufficient for a run of 25 miles over an average road with a load of 3 tons; the manufacturers state that the cost of hauling this load amounts to 1d. per kilometer.
Great care has been taken as to the quality of the steel employed in the frame and other parts of the machine. By reference to Fig. 10 it will be seen that the boiler (2) is surrounded by the fuel tank, while the water reservoir forms a seat; the motor (1) is placed beneath the platform as usual. The driver has all the controlling levers conveniently at hand; the starting lever is shown at 9, while at 5 is a small wheel controlling the steam admission; the reversing gear is actuated by the lever, 7. The vehicle is steered by means of a turning bar, similar to those of hand brakes on some wagons; the feed pump is started and stopped by a small wheel marked 10, while 8 and 11 are the hand and steam brakes respectively.
We referred just now to the tricycle made by Messrs. De Dion and Bouton, and shown by them at the competition of 1895, although it was not entered for the race. Since that time they have made two types of this class of vehicle, of which we give engravings in Figs. 12 and 13. In the former the motor is attached to the back of the frame by a suspended connection. It will be seen that the frame is not a little complex, and necessarily so, in order that it may carry the different parts of the mechanism. The motor has a single cylinder and is quite inclosed in a casing that is kept filled with oil; the moving parts of the engine are within this casing; the main shaft drives, by means of a pinion, the differential gear that is mounted on the axle. It will be seen from the illustration that the builders do not rely wholly on the motor, but have provided the usual cycle pitched chain so that, in the event of a breakdown, the rider can propel his machine with the pedals. Indeed, this is always necessary in starting, though a few strokes with the pedals suffice, and as soon as the engine is started the pedal clutch is thrown out of gear. In mounting a steep gradient the pedals are also useful as an auxiliary to the motor. The mechanical power provided is sufficient to drive the machine on a good and level road at the rate of 20 kilometers an hour. It can also travel up grades of 1 in 20 or 25; the weight of the machine in working order is only 100 lb.
On referring to the engraving there will be seen attached to the frame beneath the saddle a rectangular reservoir that contains the gasoline, the capacity being sufficient for a six hours' run. To the reservoir is attached the carburetor, which is connected to the motor by a pipe. The explosive mixture in the cylinder is fired electrically, and for this purpose a compact and reliable battery is hung to the forward part of the frame almost beneath the steering bar. This battery will give 100 hours of work without recharging; it supplies current to a Ruhmkorff coil placed beneath the rear bar of the frame in a metal case that can be seen in the engraving; the other cylinder near it is a pressure reducer into which the gases from the cylinder are exhausted before they pass into the air. The second type of tricycle, illustrated by Fig. 13, is an improvement on the first. It will be seen that the frame is much simpler; the total weight is reduced; the gasoline reservoir is triangular, in order to economize space. The motor employed is very ingenious, and appears to be efficient; we have seen it in operation at the works of MM. De Dion and Bouton. It can be run easily at a speed of 2,500 revolutions, although in practice the rate is limited to 700 revolutions, in order to reduce the wear of the moving parts. In this, as in the earlier type, the use of water for cooling the cylinder is avoided, the outside of the latter being made with a number of wings that are intended to keep the cylinder cool by contact with the air. The method of igniting the gases has also been changed, in so far as the arrangement of the battery is concerned. The four cells used for this purpose are carried in a leather case hung to one of the frames of the machine. An interesting detail is that the exact moment for producing the spark is regulated by the motor itself, and the Ruhmkorff coil is suppressed. The contact breaker has been placed on the motor, and a cylindrical cam is mounted on the shaft that controls the exhaust valve. In this cam there is formed a recess into which the blade of the contact breaker, which is fixed on an insulated mount, falls at the proper instant; at the same moment the spark is produced, the blade being raised as it leaves the recess in the cam. It is, of course, necessary to regulate exactly the relative positions of the blade and the cam, so that the spark may take place when the mixture has to be exploded. The frame of the motor is of aluminum, by which considerable saving in weight is effected; as in the earlier model, the moving parts of the motor are immersed in an oil bath. The pedals are employed to start, or as an auxiliary, or in the event of a breakdown. When not required for propulsion, they are thrown out of gear, when they serve as foot rests, and also as a means for actuating an emergency brake. The carburetor is no longer attached to the gasoline reservoir, but is separate; the explosions in the cylinder are regulated by a lever close to the steering bar.
The greatest credit must be accorded to MM. De Dion and Bouton for the perseverance and ingenuity they have shown in the design and construction of the types of power vehicle they have made their own. As to their larger carriages, experience has proved their practical value; they have expended even more trouble on their power cycles, but it appears to us that ingenuity and skill are largely wasted in this direction, since the raison d'etre of the cycle in all its forms lies in the fact that it should give perfect freedom to the rider and leave him dependent for his progress upon his own efforts.—Engineering.
The rowboat Fox, of the port of New York, manned by George Harbo, thirty-one years of age, captain of a merchantman, and Frank Samuelson, twenty-six years of age, left New York for Havre on the 6th of June. Ten days later the boat was met by the German trans-atlantic steamer Fürst Bismarck proceeding from Cherbourg to New York. On the 8th, 9th and 10th of July, the Fox was cast by a tempest upon the reefs of Newfoundland. The two men jumped into the sea, and thanks to the watertight compartments provided with air chambers fore and aft, it was possible for them to right the boat; but the unfortunates lost their provisions and their supply of drinking water. On the 15th they met the Norwegian three masted vessel Cito, which supplied them with food and water. The captains of the vessels met with signed the log book and testified that the boat had neither sail nor rudder. The Fox reached the Scilly Islands on the 1st of August, having at this date been on the ocean fifty-five days. It arrived at Havre on the 7th of August.
The Navigators of the FoxTHE NAVIGATORS OF THE FOX.
Cost what it might, the men were bent upon reaching this port in order to gain the reward promised by Mr. Fox, of the Police Gazette. Thanks to the wind and a favorable current, they made 125 miles in 24 hours. One slept three hours while the other rowed. Their skins and faces were tumefied by the wind, salt water and sun; the epidermis of their hands was renewed three times; their legs were anchylosed; and they were worn out.
The Rowboat FoxTHE ROWBOAT FOX.
The boat was 18 feet in length, 5 in breadth, and 23 inches in depth, and carried a small kerosene stove for cooking.—L'Illustration.
Burdensome as are the restrictions imposed upon shipowners by legislation, considerable justification is found for them when we compare the percentage of British vessels lost at sea with that of foreign-owned vessels. The great shipping countries, that is, those which have more than 1,000,000 tons afloat, are the United Kingdom, the British colonies, the United States of America, France, Germany and Norway. Of these six the United Kingdom suffered the least comparative loss in its mercantile fleet in 1895. Under all the heads of abandoned at sea, broken up or condemned, burnt, collision, foundered, lost, missing and wrecked, the total loss was 2.99 per cent. of the vessels owned and 2.36 per cent. of the tonnage owned. No other of the countries named has less than 3 per cent. of loss, while only the British colonies have less than 4, as the subjoined table shows.
When we turn from the contemplation of the complete fleets, and differentiate between steam and sail, we find that the United Kingdom no longer holds the premier position, being surpassed, as regards steam, both by the colonies and by the United States. Steam vessels are safer than sailing craft all over the world, partly, of course, because their average age is less. The losses they suffered last year are as follows:
The United Kingdom here stands third in the list, and curiously it only stands second under the head of number of sailing ships lost, while it is first as regards sailing tonnage lost. The sailing tonnage of the United Kingdom is only about 20 per cent. of the total, while in the colonies it is about 52 per cent. The following are the figures:
The losses of sailing vessels are very serious among the Continental nations, especially in Germany, where more than one in nine was lost or condemned last year. This is greatly due to the fact that our old ships are largely sold to the foreigner when they will no longer comply with legislative conditions of this country. We break up a few, but only 0.75 per cent., against 1.75per cent. for Norway and 2.5 per cent. for France and Germany. We are more chary of breaking up our steamers; last year only 0.46 per cent. met this fate here, 0.34 per cent. in the colonies, 0.32 per cent. in the United States, 0.86 per cent. in France, 0.31 per cent. in Germany, while Norway did not lose a single steamer in this way.
Turning now to the present year we find that in the first quarter the vessels lost, condemned or reported missing before August 7 were, according to returns made out by Lloyd's Register of British and Foreign Shipping, 282 vessels, of an aggregate of 195,480 tons. These figures are respectively 23 per cent. and 24 per cent. of the total losses last year, thus showing a favorable beginning, for the winter losses are naturally the heaviest. The materials of the vessels lost were: Steel, 24 vessels of 40,474 tons; iron, 74 vessels of 78,314 tons; and wood and composite, 184 vessels of 76,692 tons. The United Kingdom shows best under the heads of total losses and losses of sailing vessels, but in steamers it actually comes last among the six nationalities we have selected for comparison. It must be remembered, however, that the British fleet is large enough for a very fair average to be attained in three months, while in all other fleets a single loss, more or less, makes a great difference to the figures of merit. The steam tonnage of the United Kingdom is more than seven times greater than that of Germany, which is our chief competitor. In sailing tonnage we do not hold this immense superiority, our amount being only about double that of the United States and of Norway respectively.
When we examine the various causes of loss of vessels at sea, we find nearly 43 per cent. of the tonnage under the head of "wrecked," which includes vessels lost through stranding, or through striking rocks, sunken wrecks, etc. Next come 22 per cent. broken up or condemned; 14 per cent. lost, missing; 8 per cent. lost by collision; 4.3 per cent. burnt; 5 per cent. abandoned at sea; and 3.6 per cent. foundered. The following table shows the mercantile marine of the world, according to Lloyd's Register, at the end of March, 1896:
—Engineering.
[1]Gross tonnage for steamers; net for sailing vessels.
[1]Gross tonnage for steamers; net for sailing vessels.
During recent years an interesting change has been gradually brought about in the various methods of building construction employed in France, and more especially at Paris, where the size and importance of public buildings and the many-storied houses divided up into flats necessitate special systems of construction, which possess the advantages of combining economy in cost with strength and durability. Parisian architects and builders, although far from approving the extremes to which their American confrères go in the employment of iron for the construction of their somewhat exaggerated sky-scraping buildings, in which the style of architecture employed is often scarcely logical or consistent with the modern methods of construction, are nevertheless obliged to own to the necessity and the utility of employing iron in moderation for the framework of their buildings. Up to the present the use of iron in its ordinary form has chiefly been confined to floors, partitions, and roofs, where, as a rule, its presence is masked by coverings of cement, wood, or stone, except in recent examples of the new style of buildings destined for brasseries or drinking halls, where the iron construction is left visible, and emphasized by means of bronze or color painting and mosaic work, or, again, in the few examples of well known work where the architect has endeavored to obtain a decorative effect by means of iron lintels and columns. But where the use of iron is fast finding favor at Paris is in its employment in combination with other materials such as cement or concrete, and in a special form known as the cement armé systems, in which iron or steel is employed in the form of thick wire, trellis, or light bars embedded in cement or concrete. This method of construction, of which there are three different systems, has for some time been employed in the construction of various buildings of more or less importance, and has given proof of its strength and practical use as well as its advantages when employed for floors, partitions, walls and roof, both as regards its conveniences for internal arrangements, its economy, and as regards the manner in which it lends itself to modern schemes of polychrome decoration.
Two of these systems have been employed by the architect of the new building now being constructed in the Rue Blanche for the Society of Civil Engineers of France. The third system is much employed by M. De Baudot in various buildings designed by this architect, an advocate of rational construction and design and the logical employment of modern building materials. It will be interesting to examine the merits of each system as employed in these buildings, together with any other points of construction worthy of remark.
The building for the Society of Civil Engineers is remarkable from several points of view as regards construction and the arrangement of plan. The façade and plans will appear in the Building News as soon as the work is completed, and will form an interesting subject for comparison with the building recently completed for the English Society of Engineers, and with that about to be commenced at New York for the American Society.
Before entering into a detailed description of the system employed, a summary idea of the plan and general scheme of construction will not be uninteresting. The architect, M. Fernand Delmas, has endeavored to construct the building on economical lines, employing to a large extent iron and those modern materials which have been tried and found fitting as regards suitability and economy; the building will cost £22,000, and it has been made a sine qua non that all the contractors shall be members of the Society of Engineers.
The length of the façade is 100 ft.; the total depth of the building is nearly equal to the frontage; the height from pavement to cornice is 60 ft. The façade is built of solid stonework throughout its length and height. The thickness of the masonry is 24 in. at the lower stories and 18 in. at the upper portion. The façade wall is really the only portion of solid masonry work in the whole building, and forms a decorative mask to the body of the building, which is constructed of a framework of iron. The chief supports of the building proper consist of four framed iron uprights, 16 in. by 16 in. rising from the basement to the roof. These uprights are solidly trussed and held together at the floor levels by strong iron girders supporting the iron joists of the upper floors and the light partitions which divide up each story. This system is at once economical and practical. The whole building is thus self-supporting, and the thick walls which would otherwise be necessary for carrying the upper floors are thus avoided.
CEMENT ARMÉ
The façade wall is built according to the system always employed at Paris, and is formed of blocks of stone roughly cut at the quarries to the outside dimensions of the proposed moulding and decorative work. As soon as the whole front is erected the work of cutting it into shape will commence, the mouldings, pilasters, and all carving work being done while the interior is being prepared. The buildings at Paris are by this means erected much more rapidly than when the stone is dressed or moulded before being put into place. Greater facilities are thus given for studying the general ensemble of the façade and the proper scale to be given to the mouldings and decoration. The stone is as a rule soft when first from the quarries, but becomes hard and durable after dressing and exposure to the air. The courtyard wall of the building is formed of light brick or metallic fillings between the iron uprights and the party walls.
The ground floor comprises a large entrance hall or vestibule, 40 ft. by 44 ft., forming, with the cloakroom, the principal staircase, the rooms for the concierge, and the area, the whole front of the building. This large vestibule is vaulted over by means of one of the systems of cement armé to be described. The floor is constructed on another similar system, and will be paved with mosaic work. The ground floor of the courtyard will be occupied by the conference hall, 50 ft. by 50 ft., to hold 300 seats. An annex, 50 ft. by 20 ft., adjoining this hall, will open on the same by a large arched bay, and may be separated from the larger hall by means of a special system of wooden soundproof roller shutters. The floor of the large hall will be a movable one, to be raised or lowered by an ingenious system of hydraulics, and capable of being placed in an inclined position for conference meetings, or raised to a horizontal position for ball room purposes.
The entresol floor will comprise a large room for meeting, smoking and conversation rooms, and a reading room, to be used as a club for the members of the society. The first floor will contain the offices of the society, a large committee room, and all conveniences. The second floor will be devoted entirely to the purposes of the important library, comprising the library proper, a room 45 ft. by 25 ft. by 17 ft. high, rising to the ceiling of the low story above, and lighted by a large semicircular bay at either end: the surrounding rooms of the height of the second floor will be destined for the librarian, catalogues, drawing office, and library offices. The third floor will be devoted entirely to the purpose of storing the books of the library, in low rooms communicating by means of the gallery overlooking the library below, which will be crossed by means of a light, iron bridge. The bookcases will be suspended from the upper floor, and will be arranged in vertical tiers hung on rollers, after the system employed at the British Museum. The roof story will be divided up into an apartment for the chief secretary, and reached by a private staircase from the ground floor. The large basement, occupying the whole of the ground surface of the building, will be used for storing the records of the society, and will contain the heating apparatus, stores, etc. A hydraulic lift will afford access to the landings of each floor. The chief feature of the façade, which is simple in style, is the wide arched bay, 24 ft. across, rising from the pavement to above the cornice; this bay will be filled in with an open decorative framework of wrought and cast iron.
Some of the most interesting points of the construction, besides the large use of iron, are the systems employed in the construction of the floor. The ground floor is built after the Coignet system, composed of light iron bars and cement; the first floor and its supporting pillars and arches is constructed after the Hennebique system of cement armé; the upper floors are formed of iron joists, filled in either with the system of light supports and plaster, much employed at Paris, or with terracotta fillings between joints. The roof is lined internally with agglomerated cork bricks, affording protection from excessive heat or cold, and the walls of the area will be lined with opaline, a vitreous material of a bluish white color, which in this case will insure cleanliness, and afford additional light; the lavatories and water closets will also be lined with the same material.
Speaking of the Hennebique system of cement armé, employed for the arches and floor of the first story, it will be interesting to illustrate the method by a few sketches, explaining the theory of this system, which has been put to practical proofs in a large number of buildings, chiefly for industrial purposes, in the north of France. The perspective section will give an idea of the construction as employed in the building for the civil engineers, a system which holds its ground well against its rivals of other methods of cement armé.—The Building News.
Belleek porcelain (frequently pronounced "Bleak" by those who do not know the derivation of the name) is a thin eggshell ware of great lightness and translucency, characterized by a creamy, or sometimes grayish, tint, and usually covered with a delicate pearly or lustrous glaze. It is in reality a variety of Parian ware, being formed in the same manner by the process called casting, or pouring diluted clay or slip of the consistency of cream into plaster moulds, which, by absorbing a part of the moisture from the portion of the liquid preparation in direct contact, retain a thin shell of partially dried clay after the superfluous contents are taken out. After standing a few minutes the thin cast can be liberated from the mould. The thickness of the walls, of course, depends upon the length of time the slip is allowed to remain in the mould before the surplus is removed. By this ingenious method cups, saucers and other forms of ware can be made almost as thin as an egg shell or a piece of heavy paper, and after being allowed to become thoroughly dry can be safely burned in the kiln. It can readily be understood that it would not be possible to make such fragile pieces by the usual processes with plastic clay, which must be of the consistency of putty or dough, on the potter's wheel or by pressing in moulds.
Belleek ware was first made at Stoke upon Trent by the eminent potter William Henry Goss, who invented the body or composition some thirty-five years ago; but it was not then known by this name. Soon after its introduction Messrs. McBirney & Armstrong induced some of Mr. Goss' workmen, including his manager, William Bromley, to join them at their porcelain works, then recently started (in 1863) in the town of Belleek, County Fermanagh, Ireland, and the art was established so successfully there that the name of the village was given to the ware which has since become so noted. The distinguishing characteristic of this beautiful product is its lustrous glazing, which varies in form from white to yellow and through graded tints to a dark leaden hue.
Mr. Goss has continued to manufacture this dainty variety of porcelain until the present time, and his factory has become one of the most noted in the British empire. Among the most popular of his productionsin this body are loving cups and little cream jugs, cups and saucers, and fairy tea sets embellished with beautifully colored crests and coats of arms of the different English cities and of prominent personages, such as Queen Elizabeth, Sir Walter Raleigh, King Henry of Navarre, Queen Victoria, the Prince of Wales, Shakespeare, Sir Walter Scott, and Robert Burns.
Of more interest, perhaps, to Americans are the porcelain tumblers which have just been produced at the same factory, bearing on the front a faithful duplication in blue and yellow enamels of the insignia of the society of Sons of the Revolution, which were made at the suggestion of a member of the society in Pennsylvania. The soft, satiny Belleek body seems to be particularly well adapted to show off to advantage the rich designs of these badges, and this suggestion will doubtless be followed by other patriotic hereditary societies in the United States.
John Hart Brewer, of Trenton, first attempted the manufacture of Belleek ware in this country. He commenced his experiments in this line in 1882, and in the following year brought over from England William Bromley and his son from the Belleek works in Ireland. Subsequently the elder Bromley joined the Willets Manufacturing Company, of the same place, and introduced the manufacture of eggshell porcelain there, and at the present time there are no less than five or six establishments in Trenton where the same class of ware is made.
Among many specialties recently introduced is a new style of decoration which has been worked out by Miss Kate Sears, a Kansas girl who studied modeling in Boston. Going to Trenton for the purpose of pursuing her studies in this direction, one day in 1891, while engaged in working over the wet Belleek, the idea of carving delicate designs in the dry clay occurred to her, and after conducting a series of experiments her efforts were crowned with success. The process of modeling which Miss Sears has originated is as follows: A vase or other piece which has been formed in the wet clay and dried is taken before it has been in the kiln, and with knives or other tools the design is cut or chiseled so as to leave the background as thin and transparent as possible when finished. As the dry Belleek, besides being thin, is extremely brittle, and crumbles easily, the carving is an exceedingly difficult operation. It is necessarily a very slow process, since at any moment the knife is liable to cut through the wall and ruin the piece.
The result of this process is a clear cut, chiseled effect, which cannot be obtained by moulding or casting, a moonlight effect of fairy like character, most beautiful in conception, and possessing marked originality. While sometimes several weeks are consumed in executing a single piece of the carved ware, Miss Sears has produced a large number of such designs, each one of which is a perfect work of art, reflecting credit upon the artist and the manufacturers.
The marks which appear on the various productions of Belleek porcelain are of considerable interest to collectors and admirers of this beautiful ware. Mr. Gross has adopted as a factory mark his family crest, a falcon rising ducally gorged, which is printed on each piece in black. The mark of the Belleek factory in Ireland, consists of the four Irish emblems, the watch tower, the hound, the harp of Erin, and the shamrock, and is printed on the ware in green or black. At the Etruria Pottery, formerly operated by Messrs. Ott & Brewer, now known as the Cook Pottery Company, the mark used on Belleek ware was a crescent bearing the name with the initials of the proprietors, "O. & B." The Willets Manufacturing Company uses for a factory mark on its decorated Belleek pieces the figure of a serpent looped in the form of a W, which is printed in red. On similar ware produced by the Ceramic Art Company is printed in red a design composed of a painter's palette and a circle inclosing the monogram C. A. C., while Messrs. Morris and Willmore, of the Columbian Art Pottery, employ a shield with the initials of the firm name, M. W.
The manufacture of Belleek ware was introduced into this country by English potters who had learned the processes at the potteries in England and Ireland, and we cannot, therefore, lay claim to originality so far as the product itself is concerned; yet, in a measure, the ware as made in America differs materially from the foreign in many respects, and has been developed in new directions, so that it has come to have distinctive characteristics of its own which entitle it to be ranked with original American productions. While our potters, perhaps, have not yet reached the high degree of elaborate modeling which characterizes some of the imported Belleek, they have already surpassed the foreign manufacturers in the simplicity and elegance of their forms and the artistic quality of their decorations, while in delicacy of coloring, in the excellence and lightness of body, the American products are not surpassed. A visit to the showrooms of the Trenton potteries will prove a revelation to those who still believe that no artistic china is made in this country.—Edwin Atlee Barber, in China, Glass and Lamps.
The instrument we are about to describe is an improvement on the hatchet planimeter and is due to Prof. Goodman, of Leeds. One form of the instrument is intended for the measurement of areas of surfaces, and the other form for the measurement of the mean height of a figure such as an indicator diagram.
London Engineering, to which we are indebted for the cuts and copy, describes the instruments as follows: The method of using the two instruments is practically the same, but for the present we shall confine our remarks to the instrument for measuring areas. In order to familiarize oneself with the peculiar action of the instrument, it will be well to get a large sheet of paper on a drawing board or a large blotting pad, and holding the instrument vertical to the paper, grasp the tracing leg very lightly indeed between the forefinger and thumb of the right hand, with the hatchet toward the left hand, as shown in Fig. 1. Then by moving the tracing point round and round an imaginary figure and allowing the hatchet to go where it pleases, it will be seen that the hatchet moves to and fro along zigzag lines, and travels sideways—the side travel being nearly proportional to the area of the figure described by the tracing point. If the tracing point be too tightly grasped, the hatchet will not move freely, and, will have a side slip. When this occurs the side travel of the hatchet ceases to be proportional to the area traced out. A loose weight is hung on the hatchet to prevent this side slip, but as soon as a little skill is attained in the use of the instrument, this weight may be dispensed with.
GOODMAN'S HATCHET PLANIMETERGOODMAN'S HATCHET PLANIMETER
When measuring the area of such a surface as that inclosed by the boundary line shown in Fig. 3, a point, A, is chosen somewhat near the center of the figure; the exact position is, however, immaterial. From the point, A, a line, AB, is drawn in any direction to the boundary; the tracing point of the planimeter is now placed at A, with the hatchet at X, Fig. 3, that is, with the instrument roughly square with AB. The hatchet is now lightly pressed in order to mark its position on the paper by making a slight dent, then leaving the hatchet free to move as shown in Fig. 1, the tracing point is caused to traverse the line, AB, and the boundary line in a clockwise direction, as shown by the arrows, returning to A via AB. The hatchet will now be found to have taken up a new position, Y, which must be marked by again pressing the hatchet to make a slight dent in the paper. If the figure under measurement be on a separate sheet of paper, the paper must now be revolved about the point, A, through about 180 deg. (by eye), using the tracing point of the instrument as a center, care being taken that neither the point nor the hatchet be shifted while the paper is being turned. The line, AB, will again be roughly at right angles to the instrument, but in the reverse direction (see dotted lines in Fig. 3). Again cause the tracing point to traverse the line, AB, and the boundary line as before, but this time in a contra-clockwise direction. The hatchet after this backward motion will take up the new position, X1, which may or may not coincide with X; if not, prick a central point between X and X1, as shown, then, of course, the distance of this point from Y is the mean side shift of the hatchet; this distance measured from the zero of the scale on the back of the instrument is the area of the figure in square inches. The scale is read in exactly the same manner as a geometrical scale on a drawing, the whole numbers being read to the right of the zero and the decimals to the left. The instrument does not profess to give results nearer than one-tenth of a square inch.
In some cases on large maps, for example, the figure cannot be turned round as indicated above; in that case the instrument itself must be turned round through 180° and two fresh dents, X¹Y¹, obtained; the area of the figure is then the mean of the two readings, XY and X¹Y¹.
When the area is large the instrument will move through a large angle, and consequently, if square with AB to start with, it will be considerably out of square at the finish. In such a case it is only necessary to see that the mean position of the instrument is square with AB.
By carefully examining the scale it will be observed (see Fig. 1) that the divisions are not equal, but that they gradually increase from zero upward; herein consists the improvement of this instrument over the ordinary hatchet planimeter invented by Knudsen, of Copenhagen, who shows in a pamphlet published by him that
Where I = the area traced out by the pointer in square inches.
c1= the distance between the dents, X and Y, in inches.
c2= the distance between the dents, X1and Y, in inches.
p = the length of the instrument from center of hatchet to point in inches.
R² = the mean square of the radii of the figure.
The making of such a calculation for every area measured is, of course, quite out of the question. The labor involved would be as great as calculating the area by the ordinate or by Simpson's method; hence it is usual to neglect that part of the formula inclosed within the square brackets, which amounts to assuming the area to be equal to the product of the mean side shift of the hatchet by the length of the instrument; this, however, involves an error too big to be neglected, and, moreover, one that is not a constant fraction of the area measured, thus:
These errors are, however, compensated for in Goodman's improved instrument by making the scale with constantly and regularly increasing divisions. If, however, the area dealt with be not a circle, the error involved in assuming that its R² is equal to the R² of a circle of equal area is so small that it is quite inappreciable on a scale which only reads to one-tenth of a square inch. If the R² for any given area were say 5 per cent. greater than that of the equivalent circle, the error involved would be 0.0016 of the whole quantity when measuring an area of 40 square niches, or 0.064 square inch, a quantity which cannot be measured on the scale. It has been proposed to use a roller and vernier to enable the readings between the dents to be measured with a greater degree of accuracy, but it will be readily seen that the instrument is not reliable to the second place of decimals, hence such refinements are only imaginary. Even with this special scale that we have described above, the inventor does not profess to get as good results as with an Amsler planimeter; he regards his instrument as equivalent to a foot rule in comparison with a micrometric gage as representing Amsler's instrument; but for a great number of purposes the foot rule is sufficiently accurate, and only when great accuracy is required will a micrometer be used, so with the two forms of planimeter. The rougher instrument has some advantages, however; there are no delicate moving parts to get out of order, and the cost is but one-fourth.
In order to ascertain the relative accuracy of various methods of measuring areas, Prof. Goodman has had a large number of irregular areas measured by his first year students within a week or so of their entering the department, before they have attained to any degree of skill in using instruments. The results were as follows. Amsler's planimeter was taken as the standard, the area measured by it being independently checked by an assistant.
In the averaging instrument for getting mean heights of figures, the length of the instrument between the hatchet and the pointer is variable. The length is set to the length of the diagram (see Fig. 2); it is then used in precisely the same manner as the planimeter described above. From what we have already said, our diagram in Fig. 5 will be perfectly clear. The mean distance between the dents is in this case the mean height of the diagram, measured on an ordinary scale, or the mean pressure in the case of an indicator diagram measured on a scale to suit the indicator spring.
Knudsen's formula given above applies equally well to this averaging instrument. Neglecting for the moment the quantity in the square brackets, we have I = c p where c = (c1+ c2)/2 but we also have I = h l where h is the mean height and l the length of the figure, therefore h l = c p; but in this instrument we make p = l. Hence h = c, or the mean height of the figure is equal to the mean distance between the dents. The quantity in the brackets is too great to be neglected, however. If we were always dealing with circles, the ratio (R/2p)² would be a constant, and numerically equal to 1/16 or 6.25 per cent. Then all we should have to do would be to use a scale 6.25 per cent. longer than the true scale. But with a long narrow figure such as an indicator diagram, this ratio is much smaller. The measurement of a large number of diagrams gave a mean value of 1/60 for diagrams 4 in. long. It is obvious that, if a diagram be shortened, this ratio will increase, for the value of R does not decrease as rapidly as p, and vice versa; hence this ratio varies approximately inversely as the length of the diagram. Taking the value of 1/60 for the 4 in. diagram, this is equivalent to saying that there is an error of 1 in 60, or 1.67 per cent., in the result, and from the formula it will be seen that the result is too great by this amount; hence, if we make the length, l, between the legs of the instrument 1.67 per cent. of 4 in., or 0.067 in. less than the length from the tracing point to the center of the hatchet, p, we shall compensate for the error on a diagram 4 in. long. But the ratio of this constant quantity 0.067 in. to thelength of the diagram also varies inversely as the length in just the same manner as the ratio R/2p, hence this method of correcting the instrument is approximately right for all lengths of diagrams. It must be remembered that if this correction were entirely neglected, it would not exceed two per cent.; hence any inaccuracy in this correction is an exceedingly small quantity, well under 1 per cent.
Whenever errors have been attributed to the instrument, on examination it has always been found that they were due to carelessness in setting the length to the diagram, or to the tracing leg having been grasped so tightly as to cause side slip.
The accuracy of the instrument may be easily demonstrated by drawing a rectangle, say about 4 in. long and 2 in. high, and finding the mean height by the averager, then by doubling the paper over and comparing its height with the mean distance between the dents, it will be found that they agree if the instrument has been carefully used.
In many quarters we know that there is a great deal of prejudice against instruments of this kind. We are quite sure, however, that if only draughtsmen and others would spend half an hour in trying them over, they would save themselves many hours of tedious labor in calculating areas by methods which are seldom as accurate as the results obtained by a planimeter in the same number of minutes.
We give herewith, from Le Genie Civil, illustrations and brief descriptions of some of the more prominent apparatus used for the manufacture of acetylene gas.
Trouvé Apparatus (Fig. 1).—The principle of the gas generator is that of the hydrogen briquet already applied by Mr. Trouvé in his portable lamp. It consists of two vessels, one entering the other. The internal vessel is provided at the bottom with a discharge pipe communicating, through a cock, with the gasometer. It carries a suspended open work basket containing the carbide of calcium. The bottom of this vessel is provided with an aperture through which it communicates with the external vessel containing the water. The latter is brought to a level in the two vessels and attacks the carbide. The acetylene formed is disengaged and enters the gasometer. At the same time, the excess of pressure forces back the water into the external vessel in suppressing its contact with the carbide. The latter, nevertheless, continues to be attacked slowly through the action of the aqueous vapor. If the cock of the apparatus now be closed, the gas will accumulate in the interior vessel and will soon escape through the aperture in the bottom in raising the column of water. Mr. Trouvé has endeavored to remedy this inconvenience by arranging the pieces of carbide in the basket in distinct layers separated by disks of glass. He has, besides, provided his apparatus with an electric alarm, designed to give warning when the holder is too full or when it is on the point of being empty.