348 ALEXANDEK VON HUMBOLDT. 



tend the publication in London. The proceeds were to be 

 shared equally by Pictet, Bonpland, and Humboldt. The issue 

 of the work was to commence with the 6 Essai sur la Geographic 

 physique cles Plantes,' and for this pamphlet, which was to 

 consist of seven or eight sheets, the sum of 2001. was to be 

 asked. Many of these arrangements, especially those relating to 

 the classification of the work, afterwards underwent consider- 

 able modification. 



Closely as Humboldt's attention was engaged by the publica- 

 tion of his travels, he yet found time to spend months together 

 in the laboratory of the Ecole Polytechnique ; where, in con- 

 junction with Gray-Lussac, he carried on a series of investiga- 

 tions on the chemical constitution of the atmosphere, and on 

 various methods of testing the purity of the air a subject 

 which had earnestly engaged his attention before he set out 

 upon his travels. He communicated the most important re- 

 sults of these labours, in a paper he read before the National 

 Institute, on the 1st Pluviose, XIII., entitled 'Memoire sur 

 les Moyens eudiornetriques et la Constitution chimique de 

 1' Atmosphere.' l Berthollet drew up a report of this work, for 

 the Section for Physics and Mathematics, and pronounced it 

 worthy of admittance into the 'Kecueildes Savants etrangers.'' 2 



Humboldt also entered into scientific investigations with 

 Biot, and communicated the results of their joint labours in a 

 Memoir ' Upon the Variations in the Earth's Magnetism in 

 different Latitudes,' which he read before the Physical and 

 Mathematical Section of the National Institute, on December 

 7, 1804. 3 In a letter from Eome to Vaughan in Philadelphia, 

 dated June 10, 1805, he mentions: 'I have read before the 

 Institute nine Memoirs, all of which are being printed.' 4 



Thus burdened with press of work, Humboldt could yet write 

 as follows to Willdenow, who had asked him. for some ferns \ 

 the letter is dated, February 1, 1805 : 



. . . . < Busy as I am with the whirl of my own occupations, 



1 < Journ. de Phys.' vol. Ix. pp. 129-158; Gilbert's 'Annalen,' vol. xx. 

 pp. 38-93. 



2 Annal. de Chim.' vol. liii. p. 239 ; Gilbert's ' Annalen,' vol. xx. p. 99. 



3 ' Journ. de Phys.' vol. lix. pp. 429-450 ; Gilbert's ' Annalen,' vol. xx. 

 pp. 257-299. 



4 De la Roquette, ' Humboldt, Correspond ance, etc.' vol. i. p. 183. 



