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



stein, not entering Churwalden, which, however, would be 

 the direct line, and which seems quite open for their en- 

 trance, but follow the course of the Albula, and enter the 

 Domleschg, without a single fragment passing to the left 

 bank of this latter valley. We again find them, already 

 mingled with the porphyroidal granites, at the foot of Galanda 

 and, as we have said, along the borders of the Rheinthal. 

 Having reached the lake of Constance, they become the cha- 

 racteristic rock throughout all the space lying between the 

 southern bank of the lake of Constance, and the southern 

 limit of the basin in St Gall and Thurgovia ; they even pass 

 to the opposite bank, where I have met with them in the 

 neighbourhood of Mersbourg, and even beyond Ittendorf, 

 on the Ravensbourg road. Still further on, on the north and 

 east side, we find them frequently, not in the state of blocks, 

 but of pebbles. 



The gneisses of Montafun descend the valley of that name, 

 where numerous blocks of very large size cover the sides of 

 the mountains to a considerable height. They occupy all the 

 rest of the basin, where they become predominant, running 

 in a northern direction, with a slight bend to the east, like 

 the preceding I'ocks. This is in the direction of Lindau and 

 Ravensbourg ; but particularly in the neighbourhood of Cha- 

 teau de la Waldbourg, where they are numerous, and of an 

 angular form. Further to the east the blocks are rather 

 rolled, and the species more varied. I have not found any 

 blocks of Montafun gneiss on the left bank of the lake of 

 Constance. 



We thus perceive, that the law of distribution is the same 

 here as in the basins of the Rhone and Reuss. The granites 

 of Ponteljas, which come from the valley of the anterior 

 Rhine, everywhere keep the left bank, and the gneiss of 

 Montafun the right bank ; the granites of Julier the centre. 

 A transverse section of the principal part of the basin, from 

 Jouschwyl on the Thour to the Chateau of Waldbourg, shews 

 us in succession the porphyroidal granites on the sides, the 

 granites of Julier, as far as the lake ; beyond the lake, the 

 gneiss of Montafun, The respective situation of these species 

 is the same as that of the valleys from which they originate 



