224 ALEXANDER VON HUMBOLDT. 



extremely heavy for use ; it does good work, but observing 

 with it is exceedingly laborious. 



' I remain here till the beginning of April. The proximity 

 of the Alps, among which I frequently make excursions not- 

 withstanding the winter, the complete solitude I can command 

 for the prosecution of my studies, and the free use of the ex- 

 cellent library of Baron von Moll, all contribute to render my 

 stay here very enjoyable. I intend shortly to publish my " In- 

 vestigations on the Atmosphere during the Winter of 1798," 

 which I think have been carried on with a chemical accuracy 

 only to be attained by one who has, like myself, been living 

 out of doors both day and night, and could test the air at all 

 hours.' 



He relates, further, that he and Buch had determined the 

 height of the Greisberg to be 2,972 feet 6 inches above the 

 level of their apartments, and expressed an intention of insti- 

 tuting upon that mountain some observations upon refraction. 

 Unfavourable weather had prevented the observation of an 

 eclipse of the moon on December 4, as well as the occultation 

 of a star on February 28 ; he had however succeeded in deter- 

 mining the latitude and the variation of the magnetic needle, 

 and had instituted some trigonometrical observations for the 

 construction of maps of greater accuracy ; he was also engaged 

 in investigating the delicate chemical changes occurring in the 

 atmosphere for the purpose of noting the phenomena of refrac- 

 tion, and to this end undertook a daily register of the density, 

 temperature, and humidity of the air, as well as of the amount 

 of electricity, oxygen, and carbonic acid present in the atmo- 

 sphere. In a letter dated Berchtesgaden, April 17, 1 he thus 

 refers among other subjects to these labours : ' When you 

 reflect how far removed this work is from the ordinary range 

 of my chemical and physiological observations, I shall hope to 

 find in you a lenient judge. Do not suppose, however, that, 

 trusting to this forbearance on your part, I shall send you any 

 hasty or uncertain observations. No ; I am seeking to deter- 

 mine only a few points, but these I am anxious to ascertain 

 with all the accuracy of which I with my heavy 12-inch sextant 

 am capable. There is no one spot in the whole of the southern 



1 ' Allgemeine geographische Ephemeriden/ vol. ii. p. 165. 



