DISTRIBUTION OF BOULDER STONES. 347 



the Jura, from the Lake of Geneva to the Lake Constance; 

 and are also found almost every where in this great prin- 

 cipal valley. They are sometimes met with 4000 feet 

 above the level of the sea, on the side of the Jura, facing 

 the Alps, and also in considerable numbers in many of 

 the valleys of the Jura itself. These blocks occur only 

 on the surface, never in any solid rock, and no one ever 

 met with them in the subjacent strata of sandstone, marl, 

 or conglomerate of the hills and valleys, interposed be- 

 tween the Alps ^nd the Jura ; but they are sometimes 

 found deep in the soil, or imbedded or surrounded with 

 the debris formed by rivers. 



The traveller is often surprised by the enormous mag- 

 nitude of these loose blocks, some of them being calcu- 

 lated to contain 50,000 cubic feet. The smaller masses 

 are distinguished from those brought down by rivers, 

 by their position, that is, their occurring on heights and 

 acclivities, where no river could ever have run. They 

 may also be confounded with blocks from decaying con- 

 glomerate ; hence it is proper to be on our guard, not on- 

 ly to distinguish these blocks from those derived from 

 conglomerate rocks, but also from the rolled masses be- 

 longing to river courses. 



The height at which they are found does not appear 

 to have any relation to their magnitude, for we often 

 find very large blocks at considerable heights, and also 

 in deep valleys ; and we also meet with small masses 

 as well in the bottoms of valleys, as high up on the 

 mountains. 



They occur sometimes in heaps, or dispersed in single 

 blocks ; but these relations have no connection with their 

 magnitude, because we often find large and small masses 



