Beport of the Besearches of M. Agassiz. 145 



this fact, following his own mode of argument, he concluded that 

 glaciers were endowed with a kind of respiration similar to 

 that of organized beings, so that they inspired air during the 

 night, and again expired it during the day. He endeavour^ 

 to classify this phenomenon in the natural order of physical 

 facts ; and hence he repeated this experiment upon air, then 

 upon air and water, because these bodies enter into the com- 

 position of the ice of glaciers, and lastly upon water alone. 

 The result which M. Nicolet obtained was that which might 

 naturally have been expected ; for he found that the rise of the 

 mercury in the tube was nothing more than the result of the 

 contraction of the air, occasioned by the greater cold of the 

 night, and also, that it was the dilatation of the air, by the 

 heat, which made it descend during the day. 



Upon carefully repeating, however, this experiment of M. 

 Hugi, in somewhat modified circumstances, we one day ob- 

 tained a diametrically opposite result. A bell -jar, of the ca- 

 pacity of a decilitre, was filled with porous ice ; it was then 

 carefully stopped, and made to communicate with a mercurial 

 trough, by means of a graduated tube whose diameter was 

 four millimetres, the divisions being millimetres. The appa- 

 ratus was carefully secured from the direct action of the solar 

 rays, and surrounded with the powdery mass composing the 

 neve. For many hours nothing was observed in the tube but 

 a slight depression of the mercury ; but about mid-day, with 

 a temperature of + 14°. 5. C. (58° F.), the mercury rose 

 1.5 cent. (2°.7 F.). During this time the ice was melting. 

 In the course of the evening the mercury rose to the extent of 

 2 cent. (3^6 F.), with a temperature of + 13° (55°.4 F) ; 

 and the ice was now nearly all melted. The apparatus now 

 continued stationary for several hours, and at sun-set the total 

 ascent was found to have amounted to four centimetres. This 

 experiment was repeated on many occasions, night and day, 

 upon the neve and on the ice, and always with the same re- 

 sult, so that we were abundantly supplied with the proof that 

 a contraction is produced in the day-time during the gradual 

 melting of the ice. This phenomenon, which is in direct op- 

 position to the observations of M. Hugi, is only explicable upon 

 the difference which exists in the density of ice and of water ; 



VOL. XXXVI. NO. LXXI. JAN. 1844 K 



