MISCELLANEOUSINTELLIGENCE.I.MECHANICALSCIENCE.◊1.On the Adhesion of Screws.—The following results, respecting the force necessary to draw iron screws out of given depths of wood, are by Mr. Bevan, and should be placed by the side of those he has given with regard to nails128.“The screws I used were about two inches in length, 0.22 diameter at the exterior of the threads, 0.15 diameter at the bottom, the depth of the worm or thread being 0.035, and the number of threads in one inch = 12. They were passed through pieces of wood exactly half an inch in thickness, and drawn out by the weights specified in the following table:Dry beech460poundsDo. Do.790Dry sound ash790Dry oak760Dry mahogany770Dry elm655Dry sycamore830“The weights were supported about two minutes before the screws were extracted.“I have also found the force required to draw similar screws out of deal and the softer woods about half the above.“From which we may infer as a rule to estimate thefullforce of adhesion, in hard wood . . .200.000dδt=f,and in soft wood . . .100.000dδt=f,dbeing the diameter of the screw; δ the depth of the worm or thread; andtthe thickness of the wood into which it is forced;—all in inches;fbeing the force in pounds to extract the same.” We may, from the above experiments, observe the approximation to perfection in the art of screw making; for had the screw been greater in diameter, there would have been a waste of material, or had it been less, it would not have been sufficiently strong, which may be proved as follows: the cohesion of wrought iron has been found, from a number of experiments, to be about 43000 lbs. per cylindrical inch; and as the smallest diameter of screw used in my experiment was 0.15, it would have been torn asunder by a force of about 968 lbs.; or if the hard wood had been about58of an inch thick into which it had been screwed, the screw would have been broken instead of forcing its passage out of the wood.—Phil. Mag. N. S.ii. 291.128See page 360, vol. xvii. of the former series of this Journal.2.Improvement in Steam-engines.—According to the valuable records kept of the duty of the steam-engines at the mines in Cornwall, a most important improvement has been effected in two[p454]instances, of engines erected by Captain Samuel Grose; dependent entirely upon attention to the smaller details of the machines. The best engines, heretofore, had not done more than raise forty millions of pounds of water one foot high, by each bushel of coals consumed, except indeed upon short occasions. In one of the cases in question, an engine at Wheal Hope, of sixty-inch cylinder, working single as usual, the duty rose to fifty, fifty-four, and fifty-five millions of pounds; and in the other, an engine of eighty-inch cylinder, at Wheal Towan, the duty rose inApril61,877,545May60,632,179June61,762,210July62,220,820August61,764,166thus exceeding by nearly fifty per cent. what had been effected before that time.3.Improved Clock.—Among the articles displayed at the first National Exhibition of the Objects of Arts and Industry, at Neufchatel, Switzerland, last year, was a clock made by F. Houriet, of Locle; in which steel was used only in the main springs and in the axes of the moveable parts; all the other parts were in brass, gold alloy, and white gold. The number of pieces in gold, gold and silver, gold and platina, is sixty-two: all the pivots turn on jewels, and the functions of the free escapements are effected also by means of pallets in precious stones. It had been supposed that the escapements and the spiral spring not being of steel, inconvenience would result from the smaller degree of elasticity, but numerous trials with favourable results have removed the objection; and it appears that gold, hardened either by hammering or other means, is more elastic than hardened and untempered steel. The clock had gone for six days, exposed to the contact of a magnet competent to lift twenty-five or thirty pounds, without suffering any derangement.—Rév. Ency.4.Method of dividing Glass by Friction.—The following method is described by Dr. Hare: “Some years ago Mr. Lukin showed me that a small phial or tube might be separated into two parts, if subjected to cold water after being heated by the friction of a cord made to circulate about it, by two persons alternately pulling in opposite directions. I was subsequently enabled to employ this process in dividing large vessels of four or five inches in diameter, and likewise to render it in every case more easy and certain by means of a piece of plank forked like a boot-jack, and also having a kerf cut by a saw, parallel to and nearly equidistant from the principal surfaces of the plank, and at right angles to the incisions productive of the fork.“By means of the fork, the glass is easily held steadily by the hand of one operator; by means of the kerf, the string, while[p455]circulating about the glass, is confined to the part where the separation is desired. As soon as the cord smokes, the glass is plunged in water, or if too large to be easily immersed, the water must be thrown upon it; the latter method is always preferable when, upon immersing the body, the water can reach the inner surface. As plunging is the most effectual method of employing the water in the case of a tube, I usually close the end which is to be immersed.”—Silliman’s Journal, xiii. 7.5.Use of Soapstone in diminishing Friction.—In a letter to Professor Silliman upon this subject, Mr. E. Bailey of Boston, says, “I understand the Soapstone has been used for this purpose in the extensive manufactories at Lowell, for about two years, and with great profit and success. Besides answering the purpose to which it is applied very much better than any other substance that can be procured, it saves a great deal of trouble and expense. It is first thoroughly pulverized, and then mixed with oil, tallow, lard, or tar, whichever may be the best adapted to the use for which it is designed. It is of course important to procure that which is free fromgrit, and it can be purified in a good degree by mixing the powder with oil, and decanting it after it has stood a few minutes. The heavier particles will form a sediment to be rejected. It is used in all kinds of machinery where it is necessary to apply any unctuous substance to diminish friction, and it is said to be an excellent substitute for the usual composition applied to carriage-wheels.”Some idea of the value of soapstone thus applied, may be formed from the following fact communicated by D. Moody, Esq., the superintendent of the tar-works on the mill-dam near this city. Connected with the rolling machine of that establishment, there is a horizontal balance-wheel, weighingfourteen tons, which runs on a step of five inches diameter, and makes from seventy-five to one hundred revolutions in a minute. About one hundred tons of iron are rolled in this machine in a month; yet the wheel has sometimes been used from three to five weeks without inconvenience, before the soapstone has been renewed. The superintendent thinks, however, that it ought to be more frequently employed.“The use of soapstone was discovered at Lowell. It has been said never to fail in producing the desired result when applied to machinery which had began to be heated, even in those cases when nothing else could be found that would answer the purpose.”—Silliman’s Journal, xiii. 192.6.On peculiar Physical Repulsions, byM. Saigey.—I intend to give in this bulletin the description of a very simple apparatus, by means of which I have made many experiments, which have conducted me to the following results:—i. All bodies exert between themselves a feeble repulsive action in ordinary circumstances. The repulsion between bismuth and[p456]antimony and the poles of a magnetic needle, is a case of this general law, and is not due to magnetism. Nor is it magnetism which occasions the direction of needles formed of other substances than iron, announced lately by M. Becquerel.ii. A very marked attraction may be observed between a cold and a heated body, or between two bodies of different temperature, whether screens be interposed or not.iii. The metallic plates in the Cabinet de Physique de Paris, intended for the repetition of M. Arago’s experiments on magnetism by rotation, contain more or less of iron capable of attracting a very mobile magnetic needle. These plates, and those of M. Arago, were made by the same person and from the same materials.iv. I believe that, in many cases, results obtained without the appreciable developement of magnetism or electricity, have been attributed to these powers; and from well-proved experiments I shall deduce new results relative to the diurnal variation of the needle, the direction of the plumb-line and the density, temperature and attraction of the planetary masses.—Bull. Univ.A. viii. 287.7.On the Magnetic Effects of Metals in Motion.—M. Seebeck has endeavoured to determine the effects of various metals in diminishing the oscillations of a magnetic needle218inches in length, and suspended by a silk fibre three lines distant from and above the plates. The oscillations were counted from an amplitude of 45° to 10°.116oscil-lationsabove aplate ofmarble112layer ofmercury2lines inthickness.106plate ofbismuth294platina0.490antimony2.089lead0.7589gold0.271zinc0.568tin1.062brass2.062copper0.355silver0.36iron0.4It is also stated that he has found, from experiments, that by alloying such metals as are magnetic, like iron, nickel, and cobalt, with other metals, which like antimony diminish the magnetic force, alloys are obtained entirely neutral in their effects; thus the alloys formed by four of antimony with one of iron, three of copper with one of antimony, and two of copper with one of nickel, produce no diminution of the number of oscillations, these amounting to 116 as with the plate of marble. These three alloys are, therefore, the best for the manufacture of compasses, those of copper and nickel being the most malleable.—Annal. des Phy. 1826. Bull. Univ.A. viii. 136.[p457]8.Duration of the Effects of Light upon the Eye.—M. Plateau of Liege has endeavoured to determine the length of time during which the impression of certain luminous rays upon the eyes remains; and has given the following results:Flame0″.242Ignited Charcoal0″.229White0″.182Blue0″.186Yellow0″.173Red0″.1849.On the Measurement of the Intensity of Light, byM. Peclet.—A very usual photometrical process is to interpose an opaque body between a white screen and the two lights to be measured, and to move the latter until the shadows produced are of equal intensity; the intensity of the lights being then as the square of their distances from the shadows they illuminate. Sometimes a translucent body, as unpolished glass or oiled paper, is used in place of an opaque one, the shades produced by transmission being observed.In both these methods, the apparent intensity of the shadow varies with the position of the observer. If the shadows are equal when observed from a point perpendicular to the white screen at the middle of the distance of the two shades, they will be no longer so on removing from that position, and the shadow nearest to the observer will always appear the darkest. These apparent variations are greater as the shadows are farther apart, or with reflected shadows as the screen is smoother, or with transmitted shadows as the interposed obstacle is more diaphanous.The explanation given of this fact is, that unpolished opaque bodies, like paper, plaster, &c. never disperse the light incident upon them, in an uniform manner, more rays passing in the direction in which regular reflexion would take place, than in any other. Hence, when two equal shadows are produced upon such a surface, either by two equal lights at equal distances, or by two unequal lights at unequal distances; the shadow nearest to the observer must necessarily appear deeper than the other, because it is enlightened by the nearest light, the rays from which are reflected in greatest abundance away from the observer; and, on the contrary, the shadow further from the observer should appear lightest, because the rays which fall on it from the furthest light are reflected in greatest abundance towards the side on which the observer stands. The reason, also, why the effect is greater as the shadows are further apart is evident; and why in every case it is reduced to nothing when the observer is in a plane perpendicular to the screen and equidistant from the two shadows.From these facts and explanations it may be concluded, that, in all photometrical measurements by reflected shadows, the screens should have all smoothness removed from them, and the two[p458]shadows brought as near together as possible, and even made to touch or over-lap; or that, when this cannot be done, the observation should be made from a point equidistant from the two shadows. As to the shadows by transmission, the apparent variations of intensity are so great for small changes in the position of the eye, as to render the method altogether inapplicable.—Bull. Univ.A. viii. 248.10.On the apparent Decomposition of White Light by a Reflecting Body when in Motion.—The following experiment is described in theMSS. of M. Benedict Prevost and published by M. P. Prevost. A ray of solar light being introduced into a darkened chamber, is to have a square piece of white paper about two inches in the side, passed across it perpendicularly to the direction of the ray. The light reflected by the paper, instead of being white, will present a small white central portion, surrounded by the seven principal colours, nearly in the order of the prismatic spectrum. When a red surface is used instead of a white one, the decomposition of the light is still more complete. When the paper has a slight blue tint, the effect is less perfect than with the white paper. With a black surface no colours appear, but a sort of smoky shade towards the middle. A single passage of the paper is sufficient, but it is necessary that it pass entirely through the ray, no part remaining in it.—Bib. Univ.—Bul. Univ.A. viii. 248.11.On the Barometer.—The following are conclusions at which M. Bohnenberger has arrived relative to the barometer: i. The surface of mercury in a tube 14.5 lines in diameter, is slightly rounded at the edge; but, at the distance of two lines from the glass, capillary depression disappears, and the surface is level. ii. The mercury in a tube 5.8 lines in diameter is convex over the whole surface, the depression being .035 of a line. iii. The depression is generally less in a vacuum than in the air, so that a syphon barometer gives results too high, and the more so as the tube is smaller. iv. Barometers constructed with tubes five lines in diameter, do not require tapping to cause them to assume their proper height; and comparatively slight blows easily make the mercury rise too high in tubes of a smaller diameter.—Annal. der Phys. und Chem.12.Easy Method of reducing Barometrical Observations to a Standard Temperature, byS. Foggo.—The expansion of mercury deduced by the different philosophers who have examined it, is given below; omitting the results of Sir G. Shuckburgh, as being rather too far from the mean of the others.Expansion of mercury, from 32° to 212° F.De Luc1-56thLavoisier and Laplace1-55.22thHalstrom1-55thDulong and Petit1-55.5thmean, 1-55.43th.[p459]For 1° of Fahrenheit’s scale, this is equal to19977.4,or .00010023: which may be called one ten-thousandth, without the most trifling error in practice. The barometric column may, therefore, be reduced to the standard temperature of 32° F. by the following simple rule, which will make a table unnecessary.Before the first three figures of the observed height place two cyphers, multiply by the temperature of the mercury −32°, and subtract the product from the observed height. Example; barometer 30.597, temperature of mercury 74°.74° − 32° = 42°.00305 × 42 = .128 and 30.597 − .128 = 30.469 the correct height.When the temperature of the mercury is lower than 32°, the temperature is to be subtracted from 32°, and the product, obtained as before, is to beaddedto the observed height. Thus, let the barometer be as before, and the temperature 15°: then 32° − 15° = 17°; .00305 × 17 = .052, and 30.597 + .052 = 30.649, the correct height.—Jameson’s Journal, 1827, p. 378.13.Diamond Lenses.—I see by the last number of the Journal of Science and the Arts, that Mr. Varley has made a Diamond Lens, and also a single microscope with such motions as enable the observer to follow an animalcule in a diagonal direction. It is very odd, but this is precisely my plan for a microscope, which I drew up about four years ago; and as I could not get any optician to undertake it, I sent it to the Society of Arts, and recommended them to offer a premium for the best diamond lens, but they returned it. I have had a microscope of this sort (made by W. and S. Jones, Holborn) about a year and a half, and it answers the purpose completely; as a person not at all used to microscopes may use a lens of160inch focus and find a small object with it, and bring any part of it into the field of view with the greatest facility, and follow the motions of an animalcule in a diagonal direction. There are some alterations and improvements, which I have since made, that have rendered it a very complete microscope; a drawing of which I could send you, if you think it would be acceptable.I am, Sir, yours, &c.G.DAKIN.Tringham, Norfolk, July9th, 1827.14.Sapphire Lenses for Single Microscopes.—As it may justly be feared that, notwithstanding the incontestable superiority of diamond lenses, the cost and difficulty attendant on their production will enhance their value beyond the reach of the public, Mr. A. Pritchard, No. 18, Pickett Street, has applied himself with indefatigable perseverance to the formation ofSapphire Lenses. The valuable experiments of Dr. Brewster have determined that the sapphire possesses a stronger refraction than any other substance capable of giving a single image (diamond excepted),[p460]while its dispersive power is only 0.026 compared to water as 0.035. Thus if a sapphire is ground in the same tool which will form a lens of glass of the160inch focus, it will come out about the1100inch focus; being almost double the power of the glass in linear amplification, and more than double in superficial; in which latter mode of estimation the powers of the glass and sapphire may be rated at 360,000 to 1,000,000. The faint blue tinge of the sapphire is not felt in thin small lenses formed of this substance, which thus come next in order to diamond ones, and form an excellentpis allerfor those who cannot come at the latter. Many of our first microscopists are already in possession of them, and have honoured them with their unqualified approbation.There is a property possessed by small single lenses formed by precious stones, which is worthy of being commented on: viz. They can be burnished fast into brass rings, and thus safely cleaned and removed at pleasure from one setting to another. The cohesion of glass is too slight to permit this operation, during which it is almost sure to burst into shivers.—C. R. G.15.On a Method of Securing and Preserving the Rowing Pins in Boats.—Dear Sir,—To remove a petty inconvenience of hourly occurrence, by some simple contrivance, is often productive of a greater mass of advantage than an invention of greater splendour, and of apparently more extensive utility.In the accompanying drawing, you have a plan for preserving that indispensable requisite in a boat, the towels, or rowing pins; the loss of which is not only very teasing, but often productive of serious inconveniences; while the practice of stealing them from each other forms a constant source of petty depredations, leading to perpetual quarrels among seamen in harbours. He who has been detained the better part of a day in the island of Sky, till half[p461]a dozen of these pins could be procured, well knows how to value that trifle, the neglect of which has caused the loss of his voyage, and might have led to that of his boat and his life also.Fixed towels cannot well be used when boats are to be hoisted in alongside, as they are subject to be broken; and they are often inconvenient in getting in water casks, as well as in many other cases. Hence, pins capable of being unshipped are preferable. These are frequently lost, and the want is not always discovered till it cannot be replaced; or else it is not replaced without loss of that time which is often so valuable at sea. Very often, also, the delay of even a minute is rendered inconvenient or even dangerous; when the boat is dragging alongside by the painter in a heavy sea, and the vessel is either drifting or standing on.The drawing requires little explanation. By pulling at the lower pin, the two upper are fixed at once, and on being unshipped they hang secure from loss; while the lower one serves us a spare towel, should any be broken. As not one boat in twenty thousand is provided with this invention, which is indeed scarcely known, it will not perhaps be found undeserving a place in yourJournal.—I am, &c.J. M.16.Cold Injection for Anatomical Preparation.—If a mixture of varnish and vermilion has a small quantity of water mixed with it, it soon sets and becomes hard. This affords an excellent composition for anatomical injection, being very beautiful and very penetrating, (so much so, that it frequently returns by the veins,) and requiring no heat to be applied to the subject. The writer of this article frequently had, in the course of his medical education, the office of preparing this injection, of which he has, however, unfortunately forgot the proportions, and the particular nature of the varnish. It was, he thinks, a spirit varnish; the water was not mixed until the instant the injection was wanted, when it was well worked up with the syringe, and immediately thrown in; in the course of a night it would have set beautifully. This particular kind of injection was invented by an American anatomist of the name of Ramsay, and preserved as a valuable secret by him for the exclusive use of his own dissecting room. The proportions, &c. of the ingredients will soon be attained by a few experiments.
1.On the Adhesion of Screws.—The following results, respecting the force necessary to draw iron screws out of given depths of wood, are by Mr. Bevan, and should be placed by the side of those he has given with regard to nails128.
“The screws I used were about two inches in length, 0.22 diameter at the exterior of the threads, 0.15 diameter at the bottom, the depth of the worm or thread being 0.035, and the number of threads in one inch = 12. They were passed through pieces of wood exactly half an inch in thickness, and drawn out by the weights specified in the following table:
Dry beech460poundsDo. Do.790Dry sound ash790Dry oak760Dry mahogany770Dry elm655Dry sycamore830
“The weights were supported about two minutes before the screws were extracted.
“I have also found the force required to draw similar screws out of deal and the softer woods about half the above.
“From which we may infer as a rule to estimate thefullforce of adhesion, in hard wood . . .200.000dδt=f,and in soft wood . . .100.000dδt=f,dbeing the diameter of the screw; δ the depth of the worm or thread; andtthe thickness of the wood into which it is forced;—all in inches;fbeing the force in pounds to extract the same.” We may, from the above experiments, observe the approximation to perfection in the art of screw making; for had the screw been greater in diameter, there would have been a waste of material, or had it been less, it would not have been sufficiently strong, which may be proved as follows: the cohesion of wrought iron has been found, from a number of experiments, to be about 43000 lbs. per cylindrical inch; and as the smallest diameter of screw used in my experiment was 0.15, it would have been torn asunder by a force of about 968 lbs.; or if the hard wood had been about58of an inch thick into which it had been screwed, the screw would have been broken instead of forcing its passage out of the wood.—Phil. Mag. N. S.ii. 291.
128See page 360, vol. xvii. of the former series of this Journal.
128See page 360, vol. xvii. of the former series of this Journal.
2.Improvement in Steam-engines.—According to the valuable records kept of the duty of the steam-engines at the mines in Cornwall, a most important improvement has been effected in two[p454]instances, of engines erected by Captain Samuel Grose; dependent entirely upon attention to the smaller details of the machines. The best engines, heretofore, had not done more than raise forty millions of pounds of water one foot high, by each bushel of coals consumed, except indeed upon short occasions. In one of the cases in question, an engine at Wheal Hope, of sixty-inch cylinder, working single as usual, the duty rose to fifty, fifty-four, and fifty-five millions of pounds; and in the other, an engine of eighty-inch cylinder, at Wheal Towan, the duty rose in
April61,877,545May60,632,179June61,762,210July62,220,820August61,764,166
thus exceeding by nearly fifty per cent. what had been effected before that time.
3.Improved Clock.—Among the articles displayed at the first National Exhibition of the Objects of Arts and Industry, at Neufchatel, Switzerland, last year, was a clock made by F. Houriet, of Locle; in which steel was used only in the main springs and in the axes of the moveable parts; all the other parts were in brass, gold alloy, and white gold. The number of pieces in gold, gold and silver, gold and platina, is sixty-two: all the pivots turn on jewels, and the functions of the free escapements are effected also by means of pallets in precious stones. It had been supposed that the escapements and the spiral spring not being of steel, inconvenience would result from the smaller degree of elasticity, but numerous trials with favourable results have removed the objection; and it appears that gold, hardened either by hammering or other means, is more elastic than hardened and untempered steel. The clock had gone for six days, exposed to the contact of a magnet competent to lift twenty-five or thirty pounds, without suffering any derangement.—Rév. Ency.
4.Method of dividing Glass by Friction.—The following method is described by Dr. Hare: “Some years ago Mr. Lukin showed me that a small phial or tube might be separated into two parts, if subjected to cold water after being heated by the friction of a cord made to circulate about it, by two persons alternately pulling in opposite directions. I was subsequently enabled to employ this process in dividing large vessels of four or five inches in diameter, and likewise to render it in every case more easy and certain by means of a piece of plank forked like a boot-jack, and also having a kerf cut by a saw, parallel to and nearly equidistant from the principal surfaces of the plank, and at right angles to the incisions productive of the fork.
“By means of the fork, the glass is easily held steadily by the hand of one operator; by means of the kerf, the string, while[p455]circulating about the glass, is confined to the part where the separation is desired. As soon as the cord smokes, the glass is plunged in water, or if too large to be easily immersed, the water must be thrown upon it; the latter method is always preferable when, upon immersing the body, the water can reach the inner surface. As plunging is the most effectual method of employing the water in the case of a tube, I usually close the end which is to be immersed.”—Silliman’s Journal, xiii. 7.
5.Use of Soapstone in diminishing Friction.—In a letter to Professor Silliman upon this subject, Mr. E. Bailey of Boston, says, “I understand the Soapstone has been used for this purpose in the extensive manufactories at Lowell, for about two years, and with great profit and success. Besides answering the purpose to which it is applied very much better than any other substance that can be procured, it saves a great deal of trouble and expense. It is first thoroughly pulverized, and then mixed with oil, tallow, lard, or tar, whichever may be the best adapted to the use for which it is designed. It is of course important to procure that which is free fromgrit, and it can be purified in a good degree by mixing the powder with oil, and decanting it after it has stood a few minutes. The heavier particles will form a sediment to be rejected. It is used in all kinds of machinery where it is necessary to apply any unctuous substance to diminish friction, and it is said to be an excellent substitute for the usual composition applied to carriage-wheels.”
Some idea of the value of soapstone thus applied, may be formed from the following fact communicated by D. Moody, Esq., the superintendent of the tar-works on the mill-dam near this city. Connected with the rolling machine of that establishment, there is a horizontal balance-wheel, weighingfourteen tons, which runs on a step of five inches diameter, and makes from seventy-five to one hundred revolutions in a minute. About one hundred tons of iron are rolled in this machine in a month; yet the wheel has sometimes been used from three to five weeks without inconvenience, before the soapstone has been renewed. The superintendent thinks, however, that it ought to be more frequently employed.
“The use of soapstone was discovered at Lowell. It has been said never to fail in producing the desired result when applied to machinery which had began to be heated, even in those cases when nothing else could be found that would answer the purpose.”—Silliman’s Journal, xiii. 192.
6.On peculiar Physical Repulsions, byM. Saigey.—I intend to give in this bulletin the description of a very simple apparatus, by means of which I have made many experiments, which have conducted me to the following results:—
i. All bodies exert between themselves a feeble repulsive action in ordinary circumstances. The repulsion between bismuth and[p456]antimony and the poles of a magnetic needle, is a case of this general law, and is not due to magnetism. Nor is it magnetism which occasions the direction of needles formed of other substances than iron, announced lately by M. Becquerel.
ii. A very marked attraction may be observed between a cold and a heated body, or between two bodies of different temperature, whether screens be interposed or not.
iii. The metallic plates in the Cabinet de Physique de Paris, intended for the repetition of M. Arago’s experiments on magnetism by rotation, contain more or less of iron capable of attracting a very mobile magnetic needle. These plates, and those of M. Arago, were made by the same person and from the same materials.
iv. I believe that, in many cases, results obtained without the appreciable developement of magnetism or electricity, have been attributed to these powers; and from well-proved experiments I shall deduce new results relative to the diurnal variation of the needle, the direction of the plumb-line and the density, temperature and attraction of the planetary masses.—Bull. Univ.A. viii. 287.
7.On the Magnetic Effects of Metals in Motion.—M. Seebeck has endeavoured to determine the effects of various metals in diminishing the oscillations of a magnetic needle218inches in length, and suspended by a silk fibre three lines distant from and above the plates. The oscillations were counted from an amplitude of 45° to 10°.
116oscil-lationsabove aplate ofmarble112layer ofmercury2lines inthickness.106plate ofbismuth294platina0.490antimony2.089lead0.7589gold0.271zinc0.568tin1.062brass2.062copper0.355silver0.36iron0.4
It is also stated that he has found, from experiments, that by alloying such metals as are magnetic, like iron, nickel, and cobalt, with other metals, which like antimony diminish the magnetic force, alloys are obtained entirely neutral in their effects; thus the alloys formed by four of antimony with one of iron, three of copper with one of antimony, and two of copper with one of nickel, produce no diminution of the number of oscillations, these amounting to 116 as with the plate of marble. These three alloys are, therefore, the best for the manufacture of compasses, those of copper and nickel being the most malleable.—Annal. des Phy. 1826. Bull. Univ.A. viii. 136.[p457]
8.Duration of the Effects of Light upon the Eye.—M. Plateau of Liege has endeavoured to determine the length of time during which the impression of certain luminous rays upon the eyes remains; and has given the following results:
Flame0″.242Ignited Charcoal0″.229White0″.182Blue0″.186Yellow0″.173Red0″.184
9.On the Measurement of the Intensity of Light, byM. Peclet.—A very usual photometrical process is to interpose an opaque body between a white screen and the two lights to be measured, and to move the latter until the shadows produced are of equal intensity; the intensity of the lights being then as the square of their distances from the shadows they illuminate. Sometimes a translucent body, as unpolished glass or oiled paper, is used in place of an opaque one, the shades produced by transmission being observed.
In both these methods, the apparent intensity of the shadow varies with the position of the observer. If the shadows are equal when observed from a point perpendicular to the white screen at the middle of the distance of the two shades, they will be no longer so on removing from that position, and the shadow nearest to the observer will always appear the darkest. These apparent variations are greater as the shadows are farther apart, or with reflected shadows as the screen is smoother, or with transmitted shadows as the interposed obstacle is more diaphanous.
The explanation given of this fact is, that unpolished opaque bodies, like paper, plaster, &c. never disperse the light incident upon them, in an uniform manner, more rays passing in the direction in which regular reflexion would take place, than in any other. Hence, when two equal shadows are produced upon such a surface, either by two equal lights at equal distances, or by two unequal lights at unequal distances; the shadow nearest to the observer must necessarily appear deeper than the other, because it is enlightened by the nearest light, the rays from which are reflected in greatest abundance away from the observer; and, on the contrary, the shadow further from the observer should appear lightest, because the rays which fall on it from the furthest light are reflected in greatest abundance towards the side on which the observer stands. The reason, also, why the effect is greater as the shadows are further apart is evident; and why in every case it is reduced to nothing when the observer is in a plane perpendicular to the screen and equidistant from the two shadows.
From these facts and explanations it may be concluded, that, in all photometrical measurements by reflected shadows, the screens should have all smoothness removed from them, and the two[p458]shadows brought as near together as possible, and even made to touch or over-lap; or that, when this cannot be done, the observation should be made from a point equidistant from the two shadows. As to the shadows by transmission, the apparent variations of intensity are so great for small changes in the position of the eye, as to render the method altogether inapplicable.—Bull. Univ.A. viii. 248.
10.On the apparent Decomposition of White Light by a Reflecting Body when in Motion.—The following experiment is described in theMSS. of M. Benedict Prevost and published by M. P. Prevost. A ray of solar light being introduced into a darkened chamber, is to have a square piece of white paper about two inches in the side, passed across it perpendicularly to the direction of the ray. The light reflected by the paper, instead of being white, will present a small white central portion, surrounded by the seven principal colours, nearly in the order of the prismatic spectrum. When a red surface is used instead of a white one, the decomposition of the light is still more complete. When the paper has a slight blue tint, the effect is less perfect than with the white paper. With a black surface no colours appear, but a sort of smoky shade towards the middle. A single passage of the paper is sufficient, but it is necessary that it pass entirely through the ray, no part remaining in it.—Bib. Univ.—Bul. Univ.A. viii. 248.
11.On the Barometer.—The following are conclusions at which M. Bohnenberger has arrived relative to the barometer: i. The surface of mercury in a tube 14.5 lines in diameter, is slightly rounded at the edge; but, at the distance of two lines from the glass, capillary depression disappears, and the surface is level. ii. The mercury in a tube 5.8 lines in diameter is convex over the whole surface, the depression being .035 of a line. iii. The depression is generally less in a vacuum than in the air, so that a syphon barometer gives results too high, and the more so as the tube is smaller. iv. Barometers constructed with tubes five lines in diameter, do not require tapping to cause them to assume their proper height; and comparatively slight blows easily make the mercury rise too high in tubes of a smaller diameter.—Annal. der Phys. und Chem.
12.Easy Method of reducing Barometrical Observations to a Standard Temperature, byS. Foggo.—The expansion of mercury deduced by the different philosophers who have examined it, is given below; omitting the results of Sir G. Shuckburgh, as being rather too far from the mean of the others.
Expansion of mercury, from 32° to 212° F.De Luc1-56thLavoisier and Laplace1-55.22thHalstrom1-55thDulong and Petit1-55.5thmean, 1-55.43th.
[p459]
For 1° of Fahrenheit’s scale, this is equal to19977.4,or .00010023: which may be called one ten-thousandth, without the most trifling error in practice. The barometric column may, therefore, be reduced to the standard temperature of 32° F. by the following simple rule, which will make a table unnecessary.Before the first three figures of the observed height place two cyphers, multiply by the temperature of the mercury −32°, and subtract the product from the observed height. Example; barometer 30.597, temperature of mercury 74°.
74° − 32° = 42°.00305 × 42 = .128 and 30.597 − .128 = 30.469 the correct height.
When the temperature of the mercury is lower than 32°, the temperature is to be subtracted from 32°, and the product, obtained as before, is to beaddedto the observed height. Thus, let the barometer be as before, and the temperature 15°: then 32° − 15° = 17°; .00305 × 17 = .052, and 30.597 + .052 = 30.649, the correct height.—Jameson’s Journal, 1827, p. 378.
13.Diamond Lenses.—I see by the last number of the Journal of Science and the Arts, that Mr. Varley has made a Diamond Lens, and also a single microscope with such motions as enable the observer to follow an animalcule in a diagonal direction. It is very odd, but this is precisely my plan for a microscope, which I drew up about four years ago; and as I could not get any optician to undertake it, I sent it to the Society of Arts, and recommended them to offer a premium for the best diamond lens, but they returned it. I have had a microscope of this sort (made by W. and S. Jones, Holborn) about a year and a half, and it answers the purpose completely; as a person not at all used to microscopes may use a lens of160inch focus and find a small object with it, and bring any part of it into the field of view with the greatest facility, and follow the motions of an animalcule in a diagonal direction. There are some alterations and improvements, which I have since made, that have rendered it a very complete microscope; a drawing of which I could send you, if you think it would be acceptable.
I am, Sir, yours, &c.
G.DAKIN.
Tringham, Norfolk, July9th, 1827.
14.Sapphire Lenses for Single Microscopes.—As it may justly be feared that, notwithstanding the incontestable superiority of diamond lenses, the cost and difficulty attendant on their production will enhance their value beyond the reach of the public, Mr. A. Pritchard, No. 18, Pickett Street, has applied himself with indefatigable perseverance to the formation ofSapphire Lenses. The valuable experiments of Dr. Brewster have determined that the sapphire possesses a stronger refraction than any other substance capable of giving a single image (diamond excepted),[p460]while its dispersive power is only 0.026 compared to water as 0.035. Thus if a sapphire is ground in the same tool which will form a lens of glass of the160inch focus, it will come out about the1100inch focus; being almost double the power of the glass in linear amplification, and more than double in superficial; in which latter mode of estimation the powers of the glass and sapphire may be rated at 360,000 to 1,000,000. The faint blue tinge of the sapphire is not felt in thin small lenses formed of this substance, which thus come next in order to diamond ones, and form an excellentpis allerfor those who cannot come at the latter. Many of our first microscopists are already in possession of them, and have honoured them with their unqualified approbation.
There is a property possessed by small single lenses formed by precious stones, which is worthy of being commented on: viz. They can be burnished fast into brass rings, and thus safely cleaned and removed at pleasure from one setting to another. The cohesion of glass is too slight to permit this operation, during which it is almost sure to burst into shivers.—C. R. G.
15.On a Method of Securing and Preserving the Rowing Pins in Boats.—Dear Sir,—To remove a petty inconvenience of hourly occurrence, by some simple contrivance, is often productive of a greater mass of advantage than an invention of greater splendour, and of apparently more extensive utility.
In the accompanying drawing, you have a plan for preserving that indispensable requisite in a boat, the towels, or rowing pins; the loss of which is not only very teasing, but often productive of serious inconveniences; while the practice of stealing them from each other forms a constant source of petty depredations, leading to perpetual quarrels among seamen in harbours. He who has been detained the better part of a day in the island of Sky, till half[p461]a dozen of these pins could be procured, well knows how to value that trifle, the neglect of which has caused the loss of his voyage, and might have led to that of his boat and his life also.
Fixed towels cannot well be used when boats are to be hoisted in alongside, as they are subject to be broken; and they are often inconvenient in getting in water casks, as well as in many other cases. Hence, pins capable of being unshipped are preferable. These are frequently lost, and the want is not always discovered till it cannot be replaced; or else it is not replaced without loss of that time which is often so valuable at sea. Very often, also, the delay of even a minute is rendered inconvenient or even dangerous; when the boat is dragging alongside by the painter in a heavy sea, and the vessel is either drifting or standing on.
The drawing requires little explanation. By pulling at the lower pin, the two upper are fixed at once, and on being unshipped they hang secure from loss; while the lower one serves us a spare towel, should any be broken. As not one boat in twenty thousand is provided with this invention, which is indeed scarcely known, it will not perhaps be found undeserving a place in yourJournal.—
I am, &c.
J. M.
16.Cold Injection for Anatomical Preparation.—If a mixture of varnish and vermilion has a small quantity of water mixed with it, it soon sets and becomes hard. This affords an excellent composition for anatomical injection, being very beautiful and very penetrating, (so much so, that it frequently returns by the veins,) and requiring no heat to be applied to the subject. The writer of this article frequently had, in the course of his medical education, the office of preparing this injection, of which he has, however, unfortunately forgot the proportions, and the particular nature of the varnish. It was, he thinks, a spirit varnish; the water was not mixed until the instant the injection was wanted, when it was well worked up with the syringe, and immediately thrown in; in the course of a night it would have set beautifully. This particular kind of injection was invented by an American anatomist of the name of Ramsay, and preserved as a valuable secret by him for the exclusive use of his own dissecting room. The proportions, &c. of the ingredients will soon be attained by a few experiments.