1830.] The Progress of Physical Discovery. 27 



on account of its influence on the phenomena of animated nature, now 

 occupied the studies of Vogel, who observed that ammoniac and phos- 

 phorus, which do not act upon each other in the dark, disengage, by the 

 solar light, phosphorated hydrogen gas, and deposit a black powder, com- 

 posed of phosphorus and ammoniac closely combined. Phosphorus does 

 nearly the same with potash. The action of the sun's rays is not always 

 alike; the red ones produce no effect upon a solution of corrosive sublimate 

 in gether, whilst the blue ones, as well as perfect light, effect upon it a 

 mutual decomposition. M. Chevreul, in his researches upon soap, found 

 that the action of potash produces among the elements of fat new modes 

 of combination : whence result substances which did not exist before in 

 their perfect forms ; and two of which, margarine (so called from its 

 resemblance to pearl), and a sort of oil or thick fluid, acquire all the pro- 

 perties of acids; that the same effects are produced by soda, alkaline earths, 

 and various metallic oxides ; that the quantity of alkali necessary to con- 

 Vert into soap a given quantity of fat, is precisely that which is enough 

 to saturate the margarine and oil produced by this fat. M. Chevreul has 

 indeed done for soap, what a larger share of attention had previously 

 done for salts ; and his inquiries are of the more importance, inasmuch 

 as they regard an article of such essential use for the practical purposes 

 of domestic economy. It was in this year, also, that our illustrious 

 countrymen, Sir H. Davy, made that most useful and ingenious inven- 

 tion of the safety lamp, for coal mines, an invention which has preserved 

 innumerable lives, and would of itself procure him immortality in the 

 annals of civilization and science. Whether we advert to his discovery 

 of nitrous oxide ; to his investigation of the action of light on the gases, 

 and on the nature of heat ; to his discrimination of proximate vegetable 

 elements ; or to his last invention of the safety lamp, we cannot but 

 lament for the great light that is now gone out. 



The very different degrees in which bodies are dilated by heat was, in 

 1816, the subject of the investigations of M. Gay-Lussac, who, in endea- 

 vouring to discover some law to indicate the rule of these degrees, set 

 out from a point variable as to temperature, but uniform as to the cohe- 

 sion of molecules viz. that where each liquid begins to boil under a 

 given pressure. Among the delicate questions in chemistry, was that of 

 the proportions in which elements can unite, so as to form combinations 

 of different degrees. It had been remarked that there were certain 

 limits marked with preference by nature, and expressed generally in 

 simple terms ; and M. Gay-Lussac now shewed that this was especially 

 the case with gaseous combinations, in respect not to their absolute 

 weight, but their volume under an equal pressure. The gas called 

 olefiant gas, which yields an oily liquid by mixture with chlorine, was 

 now further investigated by Robiquet and Colin, who found that it is as 

 chlorine, and, united directly to super-carbonated hydrogen, that chlo- 

 rine enters into the oily liquid. 



The effects of the distribution of heat on solid bodies are referable to 

 three variable qualities; viz. their capacity for caloric their internal 

 conductibility, or the greater or less facility with which heat distributes 

 itself in them and their external conductibility, or the greater or less 

 facility with which they put themselves in unison of heat with the air or 

 surrounding bodies. The first of these qualities had been long under- 

 stood ; the third had been refered, by Count Rumford, in a great mea- 

 sure to the state of the surface; and," in 1817, M. Desprets constructed a 



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