260 M. A. Guyot oh the Distribution oj Bocks 



in the neighbourhood of Niederbipp and Aai'wangen, not only 

 do blocks of granite predominate both in number and size, 

 but they are arranged in continuous bands with well-defined 

 limits, excluding everywhere all other species of rock. This 

 takes place more especially in the Neuchatelese Jura, where 

 this disposition is more distinctly exhibited than in any other 

 place. 



On the flanks of the Chaumont chain, indeed, the upper 

 limit of the erratic formation is composed of a zone of granite 

 blocks, the largest of which measures ten metres. This zone 

 is prolonged, always becoming lower to the east side, on the 

 heights of Chaumont to the foot of Chasseral, near Nods and 

 Lignieres, then by the valleys of Orvins and Vaufi'elin. It 

 is mingled with numerous blocks, but relatively of small size, 

 of the Pennine rocks. Below this first zone is an interval of 

 upwards of a thousand feet in height, altogether destitute of 

 large blocks : with difficulty we observe here and there a 

 few representatives of the Pennine rocks. But we soon meet 

 with a second zone neai'ly twenty minutes broad, which covers 

 the plateaux of Pierre-a-Bot with a quantity of blocks quite 

 as large and numerous as those of the former zone. It is to 

 this zone that Pierre-a-Bot belongs ; it is eighteen metres 

 in size, and there are a great number of others almsot of 

 equal dimension.^. This band is prolonged to the east and 

 west in all the country of Neuchutel, and forms, a little 

 above Boujeau, near Bienne, one of the finest deposites of 

 this kind to be met with on the declivities of the Jura. 



Two species of rocks only form this train of huge blocks, 

 namely, the pi'otogine of Mont Blanc, with very large crystals 

 of felspar, coming from the needles of Chamouni, and, in gene- 

 ral, the western declivity of the chain, accompanied by a kind 

 of grey gneiss or very hard mica-slate, of which I have 

 found examples in the chain of the red Aiguilles of Chamouni. 

 The inferior limit of this zone, which, in the vicinity of Neu- 

 chatel, is five hundred feet above the plain, is distinctly 

 marked. After passing it, we immediately find the arkesines, 

 chlorites, euphotides, &c., reappear. 



These two zones may be followed to a distance, to the east 

 and w est ; but they are not everywhere so distinct. The 



