SPRINGS, RIVERS, CANALS, LAKES, 



besides find ways under-ground through which it may take its course. 

 M.vGuettaid seems also much inclined to believe, that there are, in 

 these parts, subterraneous cavities through which the waters may flow; 

 and in consequence of this he reports a number of facts, all tending 

 to prove the truth of it, or at least to prove that there must be 

 hollow quarries serving for strainers to these waters. Upon which 

 occasion he goes into a discussion of this question ; Are there any 

 subterraneous rivers, and is the prepossession of some persons in 

 favour of this particular well founded 1 He .makes it appear by se- 

 veral instances which he quotes, and by many reasons which he 

 alleges, that there are at least very great presumptions in favour of 

 this opinion. We are too apt not to look beyond the exterior of 

 things: we fee! resistance upon the surface of the earth; when we 

 go deep, we often find it it compact. It is therefore hard for us to 

 imagine that it can contain subterraneous cavities sufficient to form 

 channels for hidden rivers, or for any considerable body of water ; 

 in a word, that it can contain vast caverns ; and yet every thing 

 seems to indicate the contrary. A fact that is observed in the betoirs 

 of the rivers concerning which we have spoken, and particularly of 

 the Rille, proves in some measure that there are considerable lakes 

 of waters in the mountains which limit its course ; this fact is, that 

 in winter tlie greatest part of their betoirs become springs, which 

 supply anew the river's channel with as much water as they had ab- 

 sorbed from it during the summer. Now from whence can that 

 water come, unless from the reservoirs or lakes that are inclosed in 

 mountains, which being lower than the river in summer, absorb its 

 waters, and being higher in wiuter by the rain they receive, send it 

 back again in their turn ? 



M. Guettard strengthens this conjecture by several instances that 

 render it very probable: he remarks at the same time, that this al- 

 ternate effect of the betoirs swallowing up the water and restoring 

 it again, causes perhaps an invincible obstacle to the restraining of 

 the water within the channel of the river. It has indeed been se- 

 veral times attempted to stop those cavities ; but the water returns 

 with such violence in winter, that it generally carries away the ma- 

 terials with which they were stopped. 



The river of Sap Andre is lost in part, as we have before said, in 

 the same manner as the Ithon and the Rille ; but there is something 



