352 Of the Propagation of Heat 



contents, and placed it in the window of a room heated 

 by a German stove. 



In less than an hour I perceived that the brine and the 

 (tinged) fresh water began to mix, and at the end of 24 

 hours they were intimately mixed throughout, as was 

 evident by the colour of the aqueous fluid on which the 

 oil reposed ; which now appeared to the eye to form one 

 uniform mass of a light red tint. 



I shall leave it to philosophers to draw their own con- 

 clusions from the results of this experiment. In the 

 mean time there is one fact which it seems to point out 

 that I shall just mention, which is not only curious in 

 itself, but may lead to very important discoveries. It 

 appears to me to afford strong reasons to conclude that, 

 were a lake but very deep^ its waters, near the surface, 

 would necessarily be fresh, even though its bottom should 

 be one solid mass of rock salt ! 



Would it be ridiculous to make experiments to deter- 

 mine whether the water at the bottom of some very 

 deep lakes is not impregnated with salt .'' Should it be 

 found to be actually the case, it might prove an unex- 

 haustible treasure in an inland country, where salt is 

 scarce. 



As mines of rock-salt are often found in the neigh- 

 bourhood of fresh lakes, it seems reasonable to suppose 

 that the waters of such lakes should sometimes be in con- 

 tact with strata of these mines ; and when I first began 

 to meditate on the subject, I was much surprised, not 

 that the salt water which may lie at the bottom of fresh 

 lakes should not already have been discovered, — for 

 from the first I plainly perceived that nothing could 

 happen in the ordinary course of things that could bring 

 it to the light, or even afford any grounds to suspect its 



