FRIENDS AND COADJUTOKS AT PARIS. 31 



and though he never practised as a physician, it was through 

 medical science in its various branches that he gained distinc- 

 tion in scientific research. Humboldt was so much gratified by 

 the manner in which his achievements in science were alluded 

 to by La Metherie in an essay upon his expedition to America, 

 that in his ' Confessions ' he expresses to Pictet his desire that 

 the essay should be widely circulated in England. 



Of the French chemists and physicists, those who enjoyed 

 the closest intimacy with Humboldt were Gray-Lussac, Thenard, 

 and Berthollet, facetiously termed by him, as we have already 

 .seen in a letter to Pictet, ' Potash,' ' Soda,' and 4 Ammonia.' 

 Louis-Joseph Gay-Lussac, born in 1778, was, with the excep- 

 tion of Arago, Humboldt's most intimate friend ; with him he 

 had climbed Vesuvius and had visited Berlin, with him he 

 had shared the same room at Paris, and together they had 

 instituted important magnetic observations ; Gray-Lussac had 

 been associated with Biot in his experiments upon the con- 

 stitution of the atmosphere, and in the course of the investi- 

 gations had ascended in a balloon to the height of 23,623 

 feet. The Eloge delivered on his death in 1850 by Arago before 

 the Institute has since become justly celebrated. The sobri- 

 quet of ' Potash ' was given him by Humboldt on account 

 of some elaborate investigations which he and Thenard had 

 instituted upon the constitution of the voltaic pile and on the 

 nature of potash. The remarkable manner in which Humboldt 

 first made the acquaintance of Gray-Lussac has already been 

 described in p. 343 of the first volume ; they soon after under- 

 took in concert an important work on eudiometry. 



Louis-Jacques Thenard, born in 1777, was at the age of 

 twenty appointed chemist to the Ecole Polytechnique, and 

 at twenty-five was elected to fill the Chair of Chemistry at 

 the College de France. His investigations were conducted 

 with so much zeal and accuracy, that chemical science was 

 perhaps more indebted to him than to any of his contempo- 

 raries. He died in 1857. 



Claude-Louis, Comte de Berthollet, was born in Savoy in 

 1748, and after passing through a course of medical instruction 

 -obtained the appointment of physician to the Duke of Orleans. 

 In 1780 he was elected a member of the Eoyal Academy of 



