278 M. Stiider on some Phenomena of the Diluvial Epoch, 



during my journey of this summer, there is still one which 

 appears to me deserving of the greatest attention from geolo- 

 gists. This is a large bank or range of hills which separates 

 the basin of Ivrea from that of Biella, * extending to the foot 

 of the Alps, over a length of five or six leagues, as far as 

 Santja, in the plain of Piedmont. The height of this range, 

 on the road from Mongrande to Bolengo, cannot be estimated 

 at less than a thousand feet above the neighbouring plain ; it 

 then diminishes in height as it recedes from the ridges of the 

 Alps, in such a manner that the latter, when seen at a dis- 

 tance, appear like a very uniform talus, which had been cut on 

 its two sides by the rivers which it separates. The declivity on 

 the side of Ivrea is steep, and the road therefore descends in 

 zigzags ; it is here also that the elevation of the bank or range 

 is greatest. The back of the hill is rendered very unequal 

 by longitudinal valleys, which seem to have been produced by 

 erosion, and an hour is spent in crossing from one declivity to 

 the other. The entire mass of this hill appears to be com- 

 posed of Alpine debris. Blocks of gneiss, and other rocks of 

 all sizes, many of them from 15 to 20 feet in length, with their 

 edges little worn, are scattered over the whole surface, and 

 wherever the soil itself is disclosed, nothing is to be seen but 

 unstratified gravel and sand, inclosing a great number of 

 these same blocks. If we traverse the plain of Ivrea, and 

 ascend Lessolo to the plateau of Vico and Brosso, we perceive 

 a like number of alpine blocks covering the whole of this ra- 

 ther steep declivity, which rises to a height nearly equal to 

 that of the opposite edge above the soil of the plain. It is 

 rather remarkable, that, in the same plain, this transported 

 deposit seems to have completely disappeared, and that the 

 fixed rocks, syenite and limestone, shew themselves in nu- 

 merous places. Nor is it less surprising that, at a very 

 short distance from this ancient theatre of the violence and 

 overflowing of diluvial waters, we find on the east, between 

 Biella and Masserano, and on the west, near Castellamonte, 

 tertiary hills composed of a partly moveable and partly 

 argillaceous deposit, yielding to the action of the smallest 



