in Fluids. 323 



lost when the water is deep in consequence of its whole 

 mass being cooled in this manner, we have only to com- 

 pute how much ice this Heat would melt, or how much 

 water it would heat from the point of freezing to that 

 of boiling. 



It has been shown by experiment, that any given quan- 

 tity of ice requires as much Heat to melt it as an equal 

 quantity of fluid water loses in cooling 140 degrees ; 

 consequently, the quantity of ice which might be melted 

 by the Heat given off bv any given quantity of water 

 in cooling any given number of degrees is to the given 

 quantity of water as the number of degrees which it is 

 cooled to 140 degrees. 



Hence it follows that when the temperature of the 

 water is 8 degrees above the freezing point, it gives off 



son grand ouvrage sur les montagnes les temperatures observees au fond de ces lacs 



comme suit : 



Profondeurs Temperatures du fond 



Noms des Lacs. en pieds de France. Degres de Rearaur. 



" Lac de Geneve 950 4.3 



" de Neuchatel 325 4.1 



" de Bienne 217 5-5 



" du Bourget 240 4.5 



" d'Annecy 163 4.5 



" de Thun 350 4.0 



" de Brientz 500 3.8 



" de Lucerne 600 3.9 



" de Constance 370 3.4 



Lac Majeur 335 5.4 



Temperature moyenne du fond de dix lacs 4-34, ou 4$ R." 



"II n'est peutetre aucun de nos lecteurs qui, plein des ide'es que notre auteur 

 vient de discuter, ne soit frappe de la coincidence entre cette temperature du fond 

 des lacs dans nos latitudes moyennes et celle a laquelle 1'eau atteint son minimum 

 de volume ou maximum de densite ! La permanence de cette temperature, et son 

 identite dans des lacs d'ailleurs tres-diversement situes, paroissent intimement liees 

 avec cette circonstance du minimum de volume. Mais ce n'est pas ici le lieu de 

 donner cours aux idees que pent suggerer ce rapprochement ; nous 1'indiquons a 

 1'auteur comme un objet digne de ses meditations." 



The Author of this Essay feels himself very much obliged to his ingenious and 

 respectable friend, Professor Pictet, for these interesting observations. 



