carry us beyond our limits, we are under the necessity of omitting all farther notice.

38. For an improvement in the Lamp for burning Lard and other concrete fatty matter; Norman S. Cate, Charlestown, Mass., and James H. Putnam, Malden, Mass., November 16.

The burner of this lamp consists of two flat wick tubes, with a metallic conductor between them, and held in a spring clasp, and provided with teeth or cogs on one edge, into which, the teeth of a pinion take, to move it up and down, and thus regulate its position relatively to the height of the wicks.

Claim. "I shall claim the movable metallic conductor situated between the wick tubes, and arranged in the spring collar, as described, so as to be elevated or depressed, or adjusted to any desirable position. with respect to the flame; the same being constructed and operating substantially in the manner set forth."

39. For an improvement in the Life Preserver; Napoleon Edward Guerin, New York City, November 16.

Claim. "What I claim as my invention, is the introduction of rasped or grated cork into any garment, as a life preserver."

40. For an improvement in Elliptical Carriage Springs; David E. Edwards, Boston, Mass., November 16.

Claim. "I shall not confine myself to the method described of confining the ends of the plates, but I claim as novel and of my invention, inserting between the main lower and upper plates of an elliptic spring, a double curved spring, or one forged into the shape of an oge curve, or approaching to that of the letter S, so as to divide it into two springs and increase its rigidity, at the same time superseding the use of most, if not all the ordinary back plates; the whole being substantially as above described."

41. For a mode of securing Metallic Shanks in Glass Knobs; John G. Hotchkiss, J. A. Davenport and John W. Quincy, New York City, November 16.

"In forming the knobs of glass, whether by blowing or by pressure, a cavity is left in the back part of the knob where the neck, shank, or screw is to be fastened; such cavity being so made as that by means of a fusible metal or alloy, poured into it, the neck, shank, screw, or other article prepared for the purpose, shall be securely held in place."

Claim.-"What we claim, is the securing of shanks, screws, &c., within knobs of glass, by means of a fusible metal or alloy, substanially in the manner made known."

BIBLIOGRAPHICAL NOTICE.

American Quarterly Journal of Agriculture and Science; conducted by DR. E. EMMONS and DR. A. J. PRIME. Albany, New York: Price, $3 per annum.

Among the novelties of the day, we find upon our table, the first number of a new quarterly Journal intended to be principally devoted to the interests of Agriculture, under the title "American Quarterly Journal of Agriculture and Science; conducted by Dr. E. Emmons and Dr. A. J. Prime, Albany."

Heartily do we rejoice in the appearance of this new journal and earnestly do we desire to see it as eminently successful as it deserves, believing, as we do, that to no country has Providence given greater facilities for agricultural improvements and no where have these advantages been more entirely neglected or abused. We think, however, that we have been able, of late, to see the awakening effects of the numerous journals which have already devoted themselves to this subject and we hail the appearance of a new and powerful auxiliary in this indispensable improvement. The number now before us, gives great promise of an unusually high degree of excellence; its principles, as announced in the address to the public, must, if adhered to, render it of inestimable value to our farmers; and we are peculiarly gratified to find the distinction at once drawn between the cropping fitted for our soil and climate and that suited to the vastly different circumstances which occur in Europe. The original articles are of interest, as well to the man who wishes to keep up with the progress of information as to the practical farmer. The chemical investigations of our American plants, we look upon as of very great importance, and hope that the journal may be made a medium for giving to the public similar analyses of our own soils by our own chemists. The foreign selections are judicious. In fine, we regard the appearance of this journal as of vast importance to our Agricultural interests, and hope that it will be encouraged as it should be, by our farmers throughout the country. COM. PUB.

MECHANICS, PHYSICS, AND CHEMISTRY.

On a Theoretical Rule for the Compression of Water, By DANIEL MACKAIN, M. Inst. C. E.

[Read before the Glasgow Philosophical Society.]

The extreme elasticity of air, when considered with reference both to the amount of force which we can apply to it, capable of producing important changes in its volume, without any great effort, and to the strength of the materials of which the instruments used for ascertaining its compressibility, are composed, have enabled philoso

phers to determine with considerable accuracy the ratio which it obtains between the force applied and the resulting condensation of volume.

A considerable time ago it was believed that the compressibility of air was in proportion to the pressure applied; this was subsequently proved nearly 200 years ago, by Boyle, and also by Mariotte about 50 years afterwards; and this law of compression has since been known by the name of the latter. More recently Messrs. Dulong and Arago have confirmed the accuracy of the law of Mariotte, by experiments conducted to the range of no less than 27 atmospheres beyond the common atmospheric pressure.

By means of the barometer, the density of air is found to vary according to its mass superincumbent over any given point in the atmosphere, and the numerous experiments made with this instrument, have brought to such a degree of accuracy the barometrical measurements of parts of the earth's surface protruding into the air, as to vie with measurements of their heights made by trigonometrical instruments. These degrees of density are measured by a column of mercury, and, consequently, the height of the column indicates the force of compression, and represents the height of the superincumbent mass of air.

The extent of compression which water undergoes, when subjected to force has engaged the attention of men of science for some time back. In 1762, Mr. Canton found that the addition to, or subtraction from water, of a weight equivalent to that of the atmosphere, produced at the temperature of 60° a contraction or extension of rain water of 4 millionth t part of its bulk, and of sea water at 40 millionth parts, while in mercury it only amounted to 3 millionth parts: showing that the density of the fluid operated on materially affected the results. Thus, in the case of rain water, a force equal to a column of itself 33 feet in height produced a contraction of 46 millionth parts: of sea water, a column 32 feet in height produced a contraction of 40 millionth parts: and in mercury, a corresponding column of 24 feet produced 3 millionth parts of compression. Professor Zimmerman of Brunswick, Professor Ersted of Copenhagen, the late Sir John Leslie of Edinburgh, and Mr. Perkins, have made numerous experiments that establish the fact of compression ascertained by Mr. Canton, which, at the time his experiments were published, was at variance with the opinions universally entertained on this subject. With the usual haste with which Sir John Leslie speculated on experimental results, he arrived at the conclusion "that the ocean may rest on a subaqueous bed of air," from the apparently greater degree of condensation which force can produce in air, in contrast with that which similar forces were supposed capable of producing on water.

The degree of compression of water, is, however, extremely small:

This law has been recently extended by M. Aime to a pressure of 220 atmospheres. The full account of his beautiful and ingenious experiments will be found in Annales de Chimie, 3d series, tom. VIII, (1843) page 257.

It is evident that the author of the present article is unaware of these experiments, as well as the previous ones of Sturm and Colladom.-Com. Pub

† For 4 millionth, read 46 millionth.

and the force which it is necessary to apply to it, in order to produce any appreciable degree of diminution in volume, is so great in proportion to the limit of rigidity of the materials used in experimental apparatus, that there is much room for doubt, as to whether or not the indications heretofore recorded, be not compound measures of the elasticity of water, and of the materials of which the instruments have been formed.

It has occurred to me, that if the results of the experiments were noted, in which great bulks of water were employed, but operated upon by slight forces, that a degree of compression might be ascertained, sufficient to remove much of the doubt that may at present be entertained as to the rigid accuracy of the experiments on which our ideas of the elasticity of water are at present based-further, that, in these experiments, should any analogy be discovered between the ascertained laws which govern the compression of air, and the comparative indications of compression of water, we may take the laws which repeated experiments have proved to govern the compression of air, as analogous rules for the compression of water; and, calculating from them, may compare the theoretical results which the laws would furnish, with similar conditions ascertained by experiment.

Following out this idea, it appears probable that the transmission of water and gas through long ranges of pipes, may, by the comparative forces required to propel given quantities through them, give an approximate rule for estimating their compressibility; for, if water were totally incompressible, there would undoubtedly be some difference between the quantities of air or gas transmitted through a pipe, and that of water by a corresponding force through a similar pipe-the one would accumulate in density according to the force required for its propulsion; while the movement of the other would be like a bar of iron, influenced only by friction.

In the transmission of water through long ranges of pipes, it has been ascertained that the quantity discharged by a pipe of any given diameter in length, is inversely in proportion to the square root of the length and directly proportional to the square root of the height of the column of water employed to propel it.

The comparatively recent adaptation of carburetted hydrogen gas, for the purpose of lighting towns, has required attention to the laws by which it is conveyed through pipes. Gas is usually forced through pipes, by employing a slight column of water, of a height sufficient to propel the required volume with the velocity required. Now, as already mentioned, the laws of compression of gases and air have been exactly ascertained; and it is thence evident, that even the slight compressing force usually employed for the transmission of gas, must produce an alteration in its bulk, at the place where the motion origi

nates.

The most exact observations made as to the laws by which gas is conveyed through pipes, show that in like manner as water, the quantity which a pipe can discharge, is inversely proportional to the square root of the length of the pipe, and directly proportional to the square root of the force employed to propel it. As gas, after having

been propelled through a range of pipe, and when escaping from its extremity into the air, will be only of the density due to the pressure of the atmosphere, the proportion of it at the origin of the pipe, or, as is usual in practice, that in the gas-holder, is not only of the density of the atmosphere, but is also of that further degree of compression due to the force applied for its propulsion through the pipes. In all experiments made with pressure-gauges along various lengths of pipes, this extra degree of compression is found to diminish according to the square root of the length of the pipe, thus showing a gradual relaxation of compression, and a steady progression of current.

The ascertained laws of impulsion and of retardation of gas and water being thus exactly alike, it now only remains to ascertain their measure; and if these be found proportional to their density, there appears reason to believe, that water, under proportional forces, is as compressible as air.

I shall endeavour to support these views by the following facts and deduction from them:

As water is 825 times heavier than air, the velocity communicable to air contained in a pipe by the pressure of one vertical inch of water is equal to that of 825 vertical inches, or 68 feet of air; and if gases be referred to, as their specific gravity is usually compared with that of air as 1, the height of a corresponding column of any gas equal to 68 feet divided by the specific gravity of that gas; thus, one inch of water is equal to 12 feet of gas, specific gravity .560.

In the Hydrodynamie* of Bossut, he states as the result of experiment, that an aperture of one inch in diameter, under the pressure of a column of water 10 feet in height, discharged 8574 cubic inches, or 4.96 cubic feet of water per minute.

By an experiment made at the Leith Gas Works, a hole, one inch in diameter, under the pressure of one vertical inch of water, discharged 17.7 cubic feet of gas, specific gravity 560, in the same time. Now, comparing these discharges by the square roots of their respective impelling columns, we have

✔10 feet 4.96: 122 feet: 17.33, instead of, as above, the actual discharge 17.70.

Again, Bossut reports, that a hole 2 inches in diameter, with a pressure of 11 feet 8 inches and ten lines of water discharged 13.021 cubic inches of water in 21 seconds, or at the rate of 25.52 cubic feet per minute.

It was also found at Leith, that a hole 2 inches in diameter, with a pressure of one inch of water, discharged 69.5 cubic feet of gas, specific gravity .560, per minute.

Reducing the fractions of Bossut's pressure to decimals of a foot, and resolving the pressure into columns of the respective substances we have the proportionate discharge due to these columns:

as 11.736 feet: 22.152 :: ✓ 122: 69.41

For Hydrodynamie, read Hydrodynamique.