22 M. A. Guyot on the Erratic Basin of the Rhine. 



pebbles and worn fragments, the greater number of lime- 

 stone, strongly striated, and accompanied, as usual, with a 

 greater or less quantity of mud. 



The basin of the Rhine, unlike those of the Rhone and the 

 Gothard, presents us with none of these enormous blocks 

 which surprise the geologist, and receive particular names 

 from the inhabitants of the country. The rolled blocks, 

 with their angles very much worn off, are very numerous in 

 it, especially along the sides and extreme limits. The lime- 

 stone blocks, which are in great abundance, particularly along 

 the left bank, are rounded and striated. The angular blocks, 

 and of a certain size, are found chiefly in long trains in the 

 centre of the basin. The sides of the lake of Constance are 

 even destitute of large and angular blocks to a distance 

 of many hundred feet above its level ; but the accumulation 

 of pebbles of the same species are there numerous and ex- 

 tensive. 



The space comprised between the two branches of the 

 erratic basin of the Rhine, occupied by the central mass of 

 Haut-Sentis, and bounded on the south by the chain of Kur- 

 fursten, is destitute of the erratic fragment.s of the Rhine, 

 which seem not even to have passed the Col de Wildhaus, 

 notwithstanding its inconsidei'able height of 3600 feet. The 

 first fragments appear below Wildhaus on the Rheinthal road, 

 at a height of about 3200 feet. But the Molasse and the 

 Nagelfluhe of the whole of this region, and, in particular, of 

 the valley of Toggenbourg, are covered with numerous lime- 

 stone blocks, often very angular, sometimes rolled, accom- 

 panied with considerable deposits of limestone and sand- 

 stone pebbles. These debris constitute a very characteristic 

 erratic formation, derived no doubt from the high summits 

 and valleys of Sentis and KurfUrsten ; for we often observe 

 in the blocks the fossils which characterise the shelly strata 

 of the neighbouring chains. The general movement or spread 

 appears to havi been directed to the north. The effusion 

 of these masses has no doubt been arrested or disturbed 

 by meeting with the erratic rocks of the Rhine ; but the in- 

 riuence of this basin of the Sentis is felt much beyond its ap- 

 parent limits by the extreme abundance of the blocks and 



