US THE FOKMS OF WATER IN 



neglect. Our first effort to sound the mouliu fails 

 through the breaking of our cord by the impetuous 

 plunge of the water. A lump of grease in the hollow 

 of a weight enables a mariner to judge of a sea bottom. 

 We employ such a weight, but cannot reach the bed of 

 the glacier. A depth of 163 feet is the utmost reached 

 by our plummet. 



300. From July 28 to August 8 we have watched the 

 progress of the Grand Moulin. On the former date 

 the position of the Moulin was fixed. On the 31st it 

 had moved down 50 inches ; a little more than a day 

 afterwards it had moved 74 inches. On August 8 it 

 had moved 198 inches, which gives an average of about 

 18 inches in twenty -four hours. No doubt next summer 

 upon the Mer de Glace a Grand Moulin will be found 

 thundering near Trelaporte; but like the crevasse. of 

 the Grand Plateau, already referred to (§ 16), it will 

 not be our Moulin. This, or rather the ice which it 

 penetrated, is now probably more than a mile lower 

 down than it was in 1857. 



§ 45. The Changes of Volume of Water by Heat and Cold. 



301. We have noticed upon the glacier shafts and 

 pits filled with water of the most delicafe blue. 

 In some cases these have been the shafts of extinct 

 moulins closed at the bottom. A theory has been 

 advanced to account for them, which, though it may 

 be untenable, opens out considerations regarding the 



