160 ALEXANDER VON HUMBOLDT. 



physiology of plants. ... In the winter I intend publishing 

 some of the chemical treatises which I have by me ready for 

 the press: experiments upon light 1 and nitrogen; transfor- 

 mation of morils 2 into animal fat by the application of nitric 

 acid ; a new description of barometer based upon a recently 

 discovered principle, an instrument with which some highly 

 satisfactory measurements have been obtained here ; experiments 

 with phosphorus as a eudiometer ; on two new kinds of gas, 

 oxygenised carbonic acid and azoture de phosphore oxydee. . . . 

 A work of mine in French is to be printed at Greneva, "Lettres 

 physiques a M. Pictet;" 3 it is a collection of papers contri- 

 buted by me from time to time to the National Institute, and 

 published in the Memoirs of that society. I have made several 

 experiments this summer on the respiration of plants. . . . 



' This may convince you, my dear Willdenow, that though I 

 have been less of a scribe than other people, I have certainly 

 not been less industrious. Pray see that my little godson 

 grows up quickly, that I may take him to India with me. My 

 journey is absolutely fixed. I shall continue my preparations 

 for another year or so, and provide myself with various instru- 

 ments; my plan is to spend a year or more in Italy, for the 

 purpose of studying volcanoes, then to visit Paris and England, 

 where I should like to remain another year, for above all 

 things I mean to avoid being in a hurry, and finally, when 

 all is complete, to sail in an English ship for the West Indies. 



f Should I not live to accomplish this plan., I shall at least 

 have commenced it ivith energy and made good use of the 

 position in which fortunate circumstances have placed me.' 



1 ' I consider this to be the most delicate chemical experiment I have ever 

 made.' Alexander von Humboldt to Freiesleben. 



2 \_Morc7iella esculenta, a kind of edible mushroom.] 



3 It was never published. 



