112 M. (le Heaumont on the Glacier Theory. 



that they receive into the valleys situated at their base, where 

 it accumulates until it liquefies along with that which has fallen 

 directly upon them. It thus appears that we should not ex- 

 aggerate by calculating at about 1200 millimetres the quan- 

 tity of water which flows annually from all the snowy surfaces. 



Nearly the whole of this quantity must flow otF in conse- 

 quence of superficial liquefaction, and during the six months 

 in the course of which this superficial liquefaction is percep- 

 tible, seeing that the six millimetres which can result from 

 the permanent liquefaction beneath only form a vei-y small 

 fraction of it. The quantity of water which the snow and the 

 ice of the Alps give forth during the summer ought thus to 

 amount to 200 millimetres per month, that is to say, about 

 400 times the maxiMuin quantity which the flow of internal 

 heat is capable of melting in the same period. 



Hence it results, that in winter, mere threads of water should 

 be seen issuing from glaciers, altogether disproportionate to 

 the torrents which flow during summer ; and this, indeed, is 

 the fact, according to old as well as new observations made 

 on glaciers during the winter season ; thus observation con- 

 firms the deductions afforded by the theory of heat, and is very 

 far from contradicting them, as has been supposed. The 

 quantity of water which the flow of internal heat ought to 

 produce from glaciers in winter, is even so small, that at most 

 it can account for the slender threads of water which are seen 

 running from them ; and that the latter may very well repre- 

 sent both the water of liquefaction and the spring water ; it 

 is, moreover, quite natural that this small quantity of water 

 .should be limpid. 



W'e may nevertheless remark, that however feeble may be 

 the action exercised by the flux of the internal heat on the 

 masses of snow and of ice covering the high mountains, this 

 permanent flow of heat is one of the regulators of the extent 

 of glaciers. If, the climate remaining the same, the internal 

 heat sensibly diminished, the glaciers would require to ad- 

 vance into the valleys to a considerable extent, in order 

 that the increase of liquefaction whicli would take place at 

 their extremity should compensate for the diminished lique- 



