230 MCIHAEL FARADAY — HIS LIFE AND WORKS. 



vv'liicli cliaracterized Lim, and which jDrescrvcd him from the temptation so often 

 experienced by every discoverer^ of seeing- what he wishes to see and not seeing- 

 V/hat he th'cads. 



The worhs which have issued from his brain, so well organized, are numerous 

 and varied ; they relate essentially, as wo have already stated, to chemistry and 

 electricity. Those on the latter subject are by far the most numerous and import- 

 ant ; we shall, therefore, devote to them the greater part of this notice, after giv- 

 ing a summary exposition of the others. 



I. In 1816, Davy received a specimen of native caustic lime from Tuscany. 

 He gave it to Faraday for analysis, and found that the account given was so 

 perfect that he had it printed, and accompanied it with some observations. This 

 success, by giving Faraday confidence in his own strength, encouraged him to 

 attempt other original researches. He published (in 1817 and 1818) an investi- 

 gation of the passage of gases through narrow tubes, from which it appeared 

 that the velocity of the flo-w of elastic fluids does not depend upon their density 

 alone, but also iipon their individual nature. Various other points of chemistry 

 and physics, besides those which had electricity and magnetism for their object, 

 attracted his attention from time to time throughout the whole of his scientific 

 career. Now we have a note upon the combustion of the diamond; then an 

 investigation of the sounds produced by the combustion of gases, or by the super- 

 position of a strongly-heated iron rod upon a mass of copper at the ordinary tem- 

 ])erature, (Trevelyan's experiment ;) and then, again, researches upon the limit 

 of vaporization, or upon the evaporation of mercury at low temperatures. "We 

 may notice two impoi-tant memoirs — one upon the explanation of certain ojitical 

 illusions produced by bodies in motion, the other describing some new acoustic 

 figures proceeding from the vibrations of the stratum of air in contact with the 

 surface of vibrating plates. His elegant discovery of rcgdation (that is to say, 

 of the power possessed by two fragments of ice when brought together to become 

 amalgamated by the fact of their simple contact at a temperature above 32*^ Fah- 

 renheit) followed into its consequences as it has been by Tyndall, has had a 

 much greater influence than perhaps he ever expected. In all these notices, even 

 the least important of them, we find an original idea, a new and striking point 

 of view, which enables us at once to recognize Faraday. And, in connection 

 with this, how can we omit to mention his simple and clear explanation of table- 

 turning, and the ingenious experiment by which he so clearly shows the muscu- 

 lar efibrts made unconsciously by the persons who, by laying their hands upon 

 the table, cause its movement ? 



Let us now dwell for a few moments ujion some researches of longer dura- 

 tion, the publication of which preceded, and also in great part accompanied, his 

 great works on electricity. 



In 1820 Faraday described two new compounds of chlorine and carbon. 

 One of them is solid, transparent, and colorless ; it crystallizes in little jirisms 

 and in laminae, and is obtained by exposing to the direct action of the sun bicar- 

 bouated hydrogen gas with a large proportion of chlorine. The other contains 

 less chlorine; it is liquid and ctdorless, possesses great density, and is prepared 

 by passing the former through an incandescent tul)e, from which chlorine is set 

 free. The discovery of these two compounds filled up an important gap in the 

 history of chemistry. 



Subsequently, (in 1825,) by the compression of the gas obtained from coal, 

 Faraday obtained a new compound, which, no less interesting tlian the preced- 

 ing from a scientific point of view, had besides a great industrial importance. 

 Tiiis was a bicarburet of hydrogen in a li(|uid state, which was found to be a 

 mixture of several compounds endowed with various degrees of volatility, and 

 which could be separated by distillation. Ever3^ one knows the advantage, in 

 the production of colors, derived from this by the illustrious chemist Hofmann, 

 Avhen he extracted aniline from it. 



