256 Prof. Bischof on the Temperature of 



St Bernhard* give a decrease of temperature of 2°.25 in 546 

 feet in July, and in 946 feet in December ; making a difference 

 of 400 feet between the coldest and the warmest month.f 



Equally large differences are found between different hours 

 of the day. Thus, the following results were obtained from 

 corresponding observations at the following places : — 



Col du Geant, July, J . . j 



Zurich and Rigi Culm, June,§ . ■! 



Geneva, Ziirich, and Fauthorn, from J 



11th September to 5th October,§ \ 

 In heights of 1000 to 2400 feet between 



Poppehdorf, the Siebengebirge, and 



the Hohenacht, I found, on the 28th 



March and the 1st June 1833, by 



corresponding observations, made 



every quarter of an hour of the day 



and night, 

 At the time of tlie daily maximum of 



temperature, 

 At the time of the minimum, 



• Bibliotheque Universelle, t. x., p. 173 ; t. xiv., p. 19. 



+ In the spring, on the other hand, when the snow is already melted in the 

 low valleys of the Alps, but still covers the summits of the mountains, the 

 difference of temperature between the plains and the mountains is so great, 

 that a difference of 2°.25 may sometimes be reckoned upon, in a difference of 

 height of 60 to 160 feet. During the five days which Von Humboldt and 

 Gay-Lussac spent, in the month of May, at the convent o? Mont Cents, they 

 found the thermometer constantly 27°.00 to 33°.75 lower than at Lanslebourg, 

 although the difference of height between these two places is hardly 1944 

 feet. Gilbert's Annal., xxiv. p. 22. Hugi found the temperature on the 

 Weissenstein higher than at Solothurn, in the winter of 1829-30. Kastner's 

 Archiv fur Chem. u. Meteorol., iv. p. 130. On the 6th January 1833, 1 

 found a mean temperature, from observations made every half hour from 

 sunrise to sunset, at Poppehdorf, + 23°.49, and on the Petersberg, 838 feet 

 higher, only + 23°.68. On the other hand, on the 29th December 1832, 

 I found, from simi'ar corresponding observations at Poppehdorf a.n& Burgbrohl, 

 which only lies about 250 feet higher than the former place, but six or se- 

 ven leagues to the south-east of it, a mean of + 45"'.36 for the former, and 

 -f 33°.37 for the latter place. It was just on this day that a frost set in 

 with a south-east wind, and thus, the cold air descending into the deep valley 

 of Burgbrohl, suddenly produced this great decrease of temperature between 

 the two places. 



t De Saussure, Voyages dans les Alpes, § 2050. 

 § Kamtz in roggendorff's Ann. xxvii-, 345- 



