Hot and Thermal Springs. 391 



liarly adapted. From the above train of reasoning it would 

 be expected that such lakes would freeze to the bottom in 

 winter ; bu^, according to Bieselx,* the last mentioned lake, 

 although it remains frozen during eight to nine months, is usu- 

 ally covered with ice of only 2 feet to ^ feet in thickness, f If 

 this assertion is true, it is indeed somewhat difficult to conceive 

 how water, inclosed from above with ice, and from below with 

 aground of a temperature not surpassing the freezing point, 

 should be able to remain liquid. Could the total want of mo- 

 tion in the water, after being covered with a layer of ice, be the 

 cause of its remaining liquid ? 



Such observations would, on the other hand, be a means of 

 easily ascertaining the temperature of the soil in elevated regions, 

 if that temperature were 38°. 75 or below 38°.75, for then the tem- 

 perature of the water in the depths would very nearly coincide 

 with that of the bottom of the lake. It must, however, here be 

 taken into consideration, that, if streams issuing from glaciers of 

 a temperature nearly equal to 38».75 flow into the lake, this will 

 have an influence on the temperature of the lower strata of the 

 water. During the warm season it may easily happen that streams 

 issuing from glaciers, if they fall into the lake at a certain dis- 

 tance from the glacier, should have a temperature nearly equal 

 to that of water at its maximum of density. I have also found 

 several glacier-streams of such a temperature in the month ot 

 August at a distance from their source. But if the temperature 

 of the lower strata of the water be 38°.75, and the glacier-streams 

 warmer or colder than 38°.75, they will not reach the bottom of 

 the lake. Thus, then, it may happen that lakes, in which the tem- 

 perature at the bottom is above 38°.75, and into which glacier- 

 streams of a lower temperature are emptied, may be thereby so 

 cooled down at their surface that the heat rising from the bot- 

 tom will be compensated, and consequently that the mean tem- 

 perature at the surface will not be found to exceed that of the 



Gilbert's Annalen, vol. Ixiv. p. 202. 

 t The water of this lake is also so cold throughout the rest of the year that 

 no fish can live in it. I found the temperature of the surface of the lake of 

 Dauben on the Gemmi to be 5ri3, the temperature of the air being 46° 17- 

 and that of tiie small lake on the Faulhorn at ATM\, when the temperature' 

 of the air was 3G°.0O. 



