EULOGY ON GAY-LUSSAC. 159 



He received from M. Cle'ment, a short time after his arrival, numerous sam- 

 ples of the mysterious substauce. M. Gay-Lussac learned this, aud saw 

 at a glance what mortifying criticisms affecting the honor of our exper- 

 imentalists and academies might arise from resigning the priority, the 

 result of chance aud thoughtlessness, to the investigations of a foreign 

 chemist. He went immediately to rue du Regarda, to the poor workman, 

 obtained a small amount of the matter discovered by him, set himself 

 to the task, and produced in a few days a work equally remarkable for 

 the variety, the importance, and the novelty of the results. The iodine, 

 under the searching eye of our colleague, became a simple body, fur- 

 nishing a peculiar acid by combining with hydrogen, and a second acid 

 by uniting with oxygen. The first of these acids proved, by a new exam- 

 ple, that oxygen was not the only acidifying principle, as was believed 

 for a long time. This work of Gay-Lussac upon iodine was subse- 

 quently completed ; and there are found in a very long and beautiful 

 memoir, read August 1, 1814, and published among those of the acad- 

 emy, the varied results of the investigations of our colleague. 



Every chemist who has read this work admires in it the fertility of 

 the author in varying experiments, and the soundness of judgment 

 which always guides him when necessary to interpret them and draw 

 from them general consequences. In several chapters of this very 

 remarkable work the author dwells especially upon the analogy which 

 he establishes between chlorine, iodine, and sulphur, which throws 

 great light upon several branches of the science then involved in 

 obscurity. 



DISCOVERY OF CYANOGEN. 



Prussian blue, a substance known to manufacturers and painters, had 

 been the subject of the researches of a large number of scientists, 

 among whom we will chiefly cite the academician Macquer, Guy ton 

 de Morveau, Bergman, Scheele, Berthollet, Proust, and M. Porrett. 



Guy-Lussac, in his turn, entered the lists. His results are recorded 

 in a memoir which was read before the first class of the Institute Sep- 

 tember 18, 1815. From this moment everything doubtful became a 

 certainty ; light succeeded obscurity. This memoir, one of the most 

 beautiful of which science can boast, revealed a multitude of new facts 

 of immense interest to chemical theories. Those who will read it with 

 care will see at the cost of what fatigue, with what precautious, what 

 sobriety in the deductions, what soundness of judgment, an observer 

 succeeds in avoiding false steps, and bequeathing to his successors a defi- 

 nitive work ; I mean a work which subsequent investigations will not 

 essentially modify. 



In that admirable memoir, the author first gives an exact analysis of 

 the acid which enters into the composition of Prussian blue, and which 

 was called by Guyton de Morveau prussic acid, but which was never 

 obtained, until the work of our friend, in a state of purity, but mixed 

 only with water. _ He then showed how ho succeeded in separating the 



