of leucine, also detected the presence of a homologue of it. Virchow and Frerich have also found leucine in fresh pancreatic juice and in the glands themselves. Most of these observers believe that it is a normal product of the organism; but Virchow" has observed it to form and increase after death, and consequently looks upon it as a cadaverous product. That it is found in the living organism is, however, placed beyond doubt by my observation. But on the other hand it is doubtful whether it is ever produced by the healthy action of the organs. Is proThat it is a product of decay, though formed within bably alliving tissues, is, I think, supported by the circumstance ways a that Gorup-Besanez found several of the acids of the series product C.H.O, accompanying it in the liver; and in the mother liquor of the pancreatic tissues from which the leucine was separated, he observed the characteristic smell of the same acids on the addition of sulphuric acid. In connec- Are tion with this point it would be of interest to determine tyrosine whether tyrosine and hypoxanthine, which Wolff found in and hylarge quantities in the pancreas of the ox, and Scherer in poxanthe liver of the drunkard above mentioned (he finds always hypoxanthine in all human livers), are always formed formed during putrefaction along with leucine. Gorup-Besanez during found no tyrosine in the liver of the ox, and he thinks the putrefacpresence of hypoxanthine doubtful.

of decay.

thine

tion?

of com

sweat,

Immediately after Wurtz's discovery of methylamine Probaand ethylamine, I sought for them in several diseased se- bility of cretions, but did not get any very decided results. I presence obtained, however, from the sweat of a patient suffering pound from bromidrosis, a small quantity of ammoniacal chlorides, ammowhich yielded, with bichloride of platinum and also with nias in terchloride of gold, crystalline compounds, which appeared etc. when examined under the microscope, to consist of at least three different forms of crystals. I determined the amount of platinum in the mixed salts, and found that the atomic weight of the base or bases was much higher than that of common ammonia. Here also, as in ordinary perspiration, the greatest part of the organic matter consisted of volatile acids-formic, acetic, butyric; but in addition Caproic to them, I obtained crystals of baryta salt, which had acid prowhat appeared to me the exact form of caproate of ba- present ryta. These acids, as Lehmann has shown, are not the in sweat.

"Arch. f. Path. Anat., viii., S. 335–363.

12

12 Lehrbuch der Physiologischen Chemie, 2te Auf. 1str Bd., S. 57.

bably

I.

14 B

Impor

deter

the con

dition under

products of the decomposition of the sebaceous substance. The fact of their occurring in normal sweat is apparently opposed to the idea that they are products of putrefaction; but in the present state of our knowledge, no decided opinion can be formed as to how far the presence of the acids of this series can be considered as an indication of putrefaction.

Other occupations have hitherto prevented me from purtance of suing this kind of research; and I do not know whether any one else has turned his attention to the subject. It would undoubtedly be of the greatest importance to determine the pathological conditions under which salts of ammonia are developed in the blood, etc., and whether the compound ammonias are formed in every case where common ammonia is produced. Such investigations would be very much facilitated by a good microscopical investiformed gation of the forms of the platinum, palladium, and gold in the salts of the ammonia bases, and the publication of a good series of photographic views illustrative of them.

which com

pound

ammo

nias are

blood.

Probabi

rus

It is also possible that some of the phosphorus bases lity that discovered by Paul Thenard, and which have formed phospho- the subject of a recent admirable memoir by Hofman and Cahours, may be formed by the putrefaction of the brain and nervous matter. I hope to be able to resume my exduring periments on the putrefaction of the latter bodies immethe pu- diately, and this time on a sufficient scale to enable me to separate most of the substances formed.

bases are

formed

trefaction

of the

brain.

213

SCIENTIFIC NOTICES.

PHYSICS.

1.-On the Thermal Effects of Fluids in motion. By Professor W. THOMSON and J. P. JOULE, ESQ.'

These rescarches were made on bodies moving through air with velocities carefully measured by a whirling apparatus. The thermometers in use were filled with ether or chloroform, and were so graduated as to exhibit changes of temperature in extremely small divisions of the centigrade degree. It was thus found that a thermometer having a bulb nearly one inch in length and a quarter of an inch in diameter, would have its temperature raised 1° centigrade by a velocity of 163-7 feet per second. Another thermometer with a much more voluminous bulb, had its temperature raised to a corresponding amount by a velocity of 183.5 feet per second. On wrapping the thermometers successively with paper and with metallic wires, the effect of motion on temperature was considerably increased. With wire the effect was quintupled at slow velocities, thus rendering manifest the influence of fluid friction.

The authors have, on several occasions, noticed the effect of sudden changes in the force of the wind on the temperature of a thermometer held in it. Sometimes the thermometer was observed to rise, at other times to fall, when a gust came suddenly on. When a rise occurred, it was seldom equivalent to the effect, as ascertained by the foregoing experiments, due to the increased velocity of the air. Henco they draw the conclusion that the actual temperature of a gust of wind is lower than that of the subsequent lull. This is probably owing to the air in the latter case having had its vis viva converted into heat by collision with material objects. In sheltered situations, such as one or two inches above a wall opposite to the wind, they observed that a thermometer indicates a higher temperature than it does when exposed to the blast.

'Proceedings of the Royal Society, No. 27.

2. On the Influence of Temperature on the Elasticity of Metals. By M. KUPFFER. And on the Thermal Effects of Longitudinal Compression of Solids. By J. P. JOULE, Esq.

The results obtained by M. Kupffer are printed in the Compte rendu of the Physical Observatory of St. Petersburg. He finds that heat influences both the transverse and torsional elasticity of wires and rods of different metals. The decrease of elasticity for every degree (Reaumur) of increase of temperature is calculated by a formula containing terms deduced by observing the oscillations of rods at different temperatures. Thus, for silver, he finds a decrease of elasticity of 0.000568; for wrought iron, 0.0004696; Platinum, 0.00020110; plate glass, 0.0001242; Swedish iron, 0.0004555; English rolled hoop iron, 0.0004416; copper, 0.0005570; lead, 0.0003035. With high temperatures the loss of elasticity became a little greater.

Mr. Joule finds that heat is evolved by compression, and absorbed on removing the compressing force, in every substance he experimented on. In the case of metals the results agree very closely with the formula in which the longitudinal expansion by heat under pressure is considered the same as the expansion without pressure. He found that the experimental results were generally a little in excess of those calculated, thus indicating what M. Kupffer's researches had already established, namely, that the elastic force of metals is impaired by heat. Professor Thomson has appended some valuable remarks on the alterations of temperature accompanying changes of pressure in fluids, from which it appears that pressure generally increases in a slight degree the temperature of fluids, and that this increase is greater the higher the temperature of the fluid operated upon.

3. On the Electro-Dynamic Qualities of Metals. By Professor W. THOMSON.

The author had already communicated to the Royal Society3 a description of experiments by which he found that iron, when subjected to magnetic force, acquires an increase of resistance to the conduction of electricity along, and a diminution of resistance to the conduction of electricity across, the lines of magnetization. By some experiments made recently, he has ascertained that the electric conductivity of nickel is similarly influenced by magnetism, but to a greater degree, and with a curious difference from iron in the relative magnitude of the transverse and longitudinal effects. Thus, with the same magnetic force, the effect of longitudinal magnetization in increasing the resistance, is from three to four times as great in nickel as in iron, while the diminishing effect of the

2 Proceedings of the Royal Society, No. 27, p. 564.

3 Bakerian Lecture on the Electro-Dynamic Qualities of Metals, Feb. 27, 1856, in the Philosophical Transactions.

transverse magnetization is nearly the same in the two metals. In connection with the comparison it may be observed, that nickel was found by Faraday to lose its magnetic inductive capacity much more rapidly with elevation of temperature, and must, consequently, as the author has elsewhere shown, experience a greater cooling effect with demagnetization, than iron at the temperature of the metals in the experiments above mentioned. Professor Thomson further observes, that it will be very important to test the new property for each metal at those higher temperatures at which it is very rapidly losing its magnetic property, and to test it at atmospheric temperatures for cobalt, which, as Faraday discovered, actually gains magnetic inductive capacity as its temperature is raised from ordinary atmospheric temperatures, and which, consequently, must experience a heating effect with demagnetization, and a cooling effect with magnetization.

The present experiments, from the oblong form of the specimens of the metals used, do not admit of founding a quantitative comparison upon them; but the author hopes before long to be able to make a strict comparison between the effects for iron at least, if not for nickel also, and to find for cach metal something of the law of variation of the conductivity with magnetizing forces of different strengths.-Proceedings of Royal Society, vol. viii., No. 27, p. 550.

4.-Optics and Painting.

M. Jamin has published in the Revue des Deux-Mondes during the past year some remarkable and highly interesting views on the connection of optics with the art of painting. As Mr. Ruskin's views on landscape painting have been received with considerable favour in these countries, and as many artists are more or less tinctured with the opinions of the realistic school, we thought it might prove useful to give the following abstract of these views, which we translate from that published by the Abbé Moigno in Cosmos.

When an artist desires to imitate a scene containing unequally distributed masses of light and shade, he is obliged to attribute to each of them its real value. He must, therefore, measure, or at least estimate, the brilliancy of different objects or of different surfaces, and graduate them in his copy according to the same proportional scale as in the model. For this purpose, he possesses an eye more or less exercised, which, however, as in other men, is a powerless instrument for the exact comparison of luminous intensities. He is, moreover, obstructed by the im perfection of resources of the art of painting; for nature generally presents an absolute brilliancy that no colouring could imitate. Unable to make his picture as perfect as nature, he is forced to darken it; but, for accuracy, he should at least maintain harmony and proportion of lights; that is to say, weaken all the lights in the same proportion. On this con

Nichol's Cyclopædia of Physical Science, article "Thermo-Magnetism".