M. Pasteur on Aspat'tic and Malic Acids. 275 



which the elliptic motion gradually changed from one direction 

 to the opposite one. My 19-feet pendulum, when approaching 

 one of these nodal lines, would frequently, as in the example 

 above cited, vibrate for hours without any perceptible ellipticity. 



The latitude of my house being about 51° 27'"8, the mean 

 azimuthal motion per hour, according to Foucault's theory, would 

 be 11°- 764, which exceeds only by 0°"025 the mean of these 

 three experimental results. 



It thus appears, that if sufficient care be taken in the construc- 

 tion of the centre of suspension, and the arc of vibration be con- 

 fined within very narrow limits, this beautiful experiment may be 

 successfully performed with a pendulum of veiy moderate di- 

 mensions. 



I am. Gentlemen, 



Yours very respectfully, 



Bristol, 7 Nugent Place, Thomas G Bunt. 



September 13, 1852. 



XLIV. Report on M. Pasteur's Researches on Aspartic and 

 Malic Acids. By M. Biot*. 



THE investigation of which we are about to lay an account 

 before the Academy is essentially appertaining to mole- 

 cular chemistry. It is the examination of a case of isomerism 

 the most extensive and intimate that has been yet observed, 

 and it is accompanied by striking peculiarities of an entirely 

 novel character. The phaenomena of isomerism are in themselves 

 among those which are most capable of affisrding an explanation of 

 the mechanism of chemical reactions, by giving us an opportunity 

 of investigating by comparison what are the molecular conditions 

 which render these reactions so different in substances consisting 

 of the same chemical elements united in the same proportions of 

 weight. But these abstractions, which include the whole science, 

 cannot be deduced from known facts except by a train of mecha- 

 nical and physical reasoning; the first term of which commences 

 with their most simple phajnomena, and the last terminates with 

 their most remote causes. We are therefore compelled in the 

 present case to introduce the principal links of this logical chain, 

 for the purpose of proving that the researches of M. Pasteur 

 have added new elements to our knowledge of these phsenomena. 

 If the rapid exposition which we are about to give should appear 

 in the first instance to be a digression from our proper aim, we 

 plead as an excuse that we have ineffectually endeavoured to dis- 

 cover any other method by which it could l}c attained, consist- 



* I'Vom the Comptes Rendus, vol. xxxiii. p. 54^. 



T2 



