edges of the beaters in a few minutes, and so adjusted as to scour very severely. They can be used, or not, as may be desired.

This blast, which carries off the smut, white caps, and other impurities, is generated by the same action of the beaters that scours the wheat; the air for it is supplied at the open ends of the concave, and finds an ample and unobstructed vent out of the top of the chimney, so that this machine, by one and the same action of the beaters (without any increase of power), becomes a smut mill, scourer, and extensive fan.

Particular attention is desired to this fact, that the blast carries out the smut and impurities the instant they are disengaged (which is the only proper time to be rid of them); it does not allow them to be conveyed through the body of the wheat (blackening the ends of the berries), but it is acting all the time, driving the impurities out of the chimney at each revolution, as fast as they are disengaged, by the scouring action of the beaters.

By this fan action of the machine, a current of air is always drawing into the open ends of the concave, carrying with it any dust floating in the surrounding atmosphere; hence, instead of being dirty, the contrary is the case; it cleans the room in which it runs.

In consequence of the peculiar action of this machine, throwing the wheat out of the concave at each revolution, it requires little power to drive it.

For country mills, no other cleaning apparatus is required, excepting a shaking or rolling screen, before the grain is put through this smut mill. For merchant mills, it is capable of doing the heaviest work in the most thorough manner: for its safety against fire, its durability, its efficacy as a thorough smut mill, scourer, and fan, see the following certificates.

These machines are manufactured by BEAUMONT & HOLLINGSWORTH, Zanesville, Ohio, who will promptly execute any orders that may be sent to them.*

Experiments on Charcoal.t

M. Violet, the government commissioner of gunpowder, has presented to the Institute the following observations, resulting from experiments to obtain a charcoal with a constant amount of carbon. He has experimented on seventy-five species of wood, native and foreign, but especially on the black alder (bourdaine, resprun), a sort of white timber nearly resembling prickwood (fusain), which is mostly used. If wood be carbonized, the quantity of carbon obtained is in an inverse ratio to the temperature to which it has been submitted by the process. Thus, at a temperature of 250° Reaumur, the amount of carbon is 50 per cent.; at 200° it is 33 per cent.; at 400° about 20% per cent.; and at 1500°the highest temperature obtainable, being the melting point of platinumthe amount of carbon is but. The quantity of carbon originally 206. contained in wood is separated, in the process of carbonization, into two portions, of which one remains in the charcoal, while the other passes off with like volatile substances. This separation varies according to the

• See advertisement on the cover of this Journal.

† London Architect, 1851.

temperature employed in the act of carbonisation: at 250° the carbon remaining in the charcoal is double that which has escaped; between 300° and 350° both portions are equal. Not even the highest temperature, however, could change charcoal into pure carbon. Charcoal invariably contains gas even after being exposed to the highest temperature. At 250° the quantity of gas is half the amount of carbon; at 300° one-third; at 350° one-fourth; at 400° one-twentieth; at 1500° onehundredth part. If wood is carbonized in perfectly closed vessels, it yields three times more charcoal than by the ordinary process. Treated in this way, wood undergoes a real process of fusion at a temperature of from 300° to 400°; it becomes semi-fluid, glutinous, and presents, when cooled, a black, lustrous mass, from which all organic texture has disappeared-resembling, in a word, coarse coal. This process is, after all, nothing but a repetition of that grand operation by which nature has produced those extensive strata of coal all over the globe. Charcoal obtained in close vessels contains ten times more cinders than that made in the ordinary way-a sure sign that the volatile substances of the wood carry with them a great quantity of mineral substances during the process of carbonization, although the latter be not volatile by themselves. Proceed. Paris Academy.

Method of obtaining Oxygen from Atmospheric Air. By M. BOUSSINGAULT.*

Lavoisier resolved atmospheric air into its constituents by keeping a confined portion for twelve days in contact with mercury heated nearly to its boiling-point. Boussingault has attempted to use baryta for the purpose of extracting the oxygen from the atmospheric mixture in larger proportion. The method is simple; the air is conducted over pieces of baryta at a dark red heat until it has become converted into peroxide of barium; the oxygen is subsequently again expelled by the application of a more intense heat. The moisture and carbonic acid usually present in the air do not materially interfere with the process. The baryta, however, contained so much alumina and silica, that after repeated use it became caked, and hence no longer of any use. Pure baryta was free from this inconvenience. According to Boussingault, on the large scale, on using 10 kilogrammes of baryta, which absorb 730 litres of oxygen, and should again part with it, 600 litres is the quantity always obtained in practice. Hence with furnaces in which 100 kilogrammes of baryta distributed in 8 to 10 tubes can be heated at once, from 24,000 to 30,000 litres of oxygen may be produced in twenty-four hours.-Comptes Rendus, vol. XXXII, pp. 266, 267.

Translated for the Journal of the Franklin Institute.

Deep Sea Soundings.

M. Faye, at the meeting of the Academy of Sciences of Paris, 20th January, described an apparatus which he considered as new, and presenting valuable facilities for deep sea soundings, requiring no line, and • London, Edinburgh, and Philosophical Magazine, June, 1851.

giving with accuracy the perpendicular depth and the set of the submarine currents. It consists of a stout cylinder open below, and filled with a liquid sufficiently lighter than water, to cause the apparatus to float; it is sunk by having two cannon balls attached to it, which are released by a trigger striking against the bottom, when the apparatus returns to the surface. The distance and direction of its point of emvergence from that of its sinking, will give the resultant of the submarine currents; and it has, moreover, attached to it a light fan, whose revolutions will measure the space moved over. (This is Saxton's apparatus for measuring the velocity of curren's of water.) A little vessel attached and provided with valves to close when the vessel begins to rise, will bring to the top a specimen of the bottom water, and an overflow thermometer, (on Walferdin's principle); a modification of the apparatus itself will measure the temperature. At subsequent sessions of the academy, the proposed apparatus was shewn to be not new, but it remains to be seen whether it may not prove very useful.

On some Properties peculiar to Caoutchouc, and their Applications. By MR. BROCKEDON.*

Caoutchouc is a vegetable constituent, the produce of several trees. The most prolific in this substance are, Siphonia caoutchouc Urceola elastica, Ficus elastica, &c. Of these, the Siphonia caoutchouc extends over a vast district in Central America,--and the caoutchoc obtained from this tree is best adapted for manufactures. Over more than 10,000 square miles in Assam the Ficus elastica is abundant. The Urcela elastica, (which produces the Gintawan of the Malays) abounds in the islands of the Indian Archipelago. It is described as a creeper of growth so rapid, that in five years it extends 200 feet, and is from 20 to 30 inches in girth. This tree can, without being injured, yield by tapping from 50 to 60 lbs. of caoutchouc in one season. A curious contrast is exhibited in the tardy growth of the tree from which the gutta percha is obtained. This tree does not come to its prime in less than from 80 to 120 years. The produce cannot be obtained but by the sacrifice of the tree. It is found in a concrete state between the bark and the wood after the tree has been cut down; and it is in this condition that, having been scraped out, it is sent to our market. When coagulated by evaporation or agitation, caoutchouc separates from the aqueous portion of the sap of the trees which yield it. This solid and fluid cannot afterwards be re-united, any more than butter is capable of mixing with the milk from which it is separated. Caoutchouc is a hydro-carbon. This chemical character belongs to all varieties of the substance, and many other vegetable constituents, though they differ materially in physical qualities. Some specimens are harder than gutta percha itself, while others never solidify, but remain in the condition of birdlime or treacle. The process termed the vulcanizing of caoutchouc was discovered by Mr. Thomas Hancock in 1843. A sheet of cauotchouc immersed in melted sulphur, absorbs a portion of it, and at the same time it undergoes some important changes in many of its characteristic properties. It is no longer affected by climatic temperature:-it is neither hardened by cold,

• London Athenaeum, April, 1851.

nor softened by any heat which would not destroy it. It ceases to be soluble in the solvents of common caoutchoc, while its elasticity becomes greatly augmented and permanent. The same effect may be produced by kneading sulphur into caoutchouc by means of powerful rollers; or the common solvents naphtha and spirit of turpentine may be charged with a sufficient amount of sulphur in solution to become a compound solvent of rubber. In these cases articles may be made in any required forms before heating for the change of condition. It is necessary, however, for this purpose, that the form should be carefully maintained during the exposure to the heat necessary to effect the vulcanization, which leaves it in a normal state. A vulcanized solid sphere of 23 inches in diameter when forced between two rollers a quarter of an inch apart was found to maintain its form uninjured. In fact, it is the exclusive property of vulcanized caoutchouc to be able to retain any form impressed on it, and to return to that form on the removal of any disturbing force which has been brought to act on it. Caoutchouc slightly expands and contracts in different temperatures: it is also capable of being condensed under pressure. A cube of 24 inches, impactly secured, was subjected to a force of 200 tons. The result was, a compression amounting to one-tenth; great heat appeared to have been evolved; and the excessive elasticity of the substance caused a fly-wheel weighing 5 tons to recoil with an alarming violence. The evolution of heat from caoutchouc under condensation is a property possessed by it in common with air and the metals. It differs, however, from the latter in being able to exhibit cold by re-action. Mr. Brockedon stated that he had raised the temperature of an ounce of water two degrees in about fifteen minutes by collecting the heat evolved by the extension of caoutchouc thread. He refers this effect to the change in specific gravity. He contends, that this heat thus produced is not due to friction; because the same amount of friction is occasioned in the contraction as in the extension of the substance, and the result of this contraction is to reduce the caotchouc thus acted on to its original temperature. Attention was directed to some of the latest applications of the elastic force of caoutchouc.-Proceed. Roy. Inst. March 21, 1851.

Translated for the Journal of the Franklin Institute.

Reflexion of Light from the Surface of Liquids.

The following are the conclusions of M. Jamin, from a series of experiments recorded in the Annals de Chimie et de Physique, for February, 1851:

1st, Liquids surfaces polarize light incompletely and elliptically.

2nd, Liquids having a high index of refraction have a positive anomaly, or difference of phase between the principal components of the reflected motion.

3rd, This anomaly becomes negative, when the index is very small. 4.h, There are substances, whose indices are about 14, whose polarization is rectilineal.