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On the Erratic Basin of the Rhine. By M. A. GUVOT. 

 Communicated by the Author. 



The following are the results of M. Guyot's last investiga- 

 tions of the erratic basin of the Rhine, during the autumn 

 of 1844 and the summer of 1845. 



This basin, of which we have hitherto known very little, 

 not to say nothing at all, is the most considerable after that 

 of the Rhone. It has not, like the latter, a double divergency 

 in two opposite directions. On issuing from the valley of 

 the Rhine, at the origin of the lake of Constance, it is from 

 20 to 25 leagues in breadth and equal in length, in a direction 

 of north-west and west, which is that of the lake, and it dis- 

 appears on the declivities of the Wurtemberg Jura, or Rau- 

 halp, which it nowhere exceeds in height. We may, therefore, 

 affirm in the present day, that the line of the Jura has served 

 as a banner to the Alpine erratic formation, throughout its 

 whole length ; that this formation has never passed over it, 

 not even in the region where the conflux of the Aar and 

 Rhine takes place, although, at this point, the chain under- 

 goes so considerable a diminution in height that it may al- 

 most be called a gap. 



Limits. — The erratic rocks of the basin of the Rhine are 

 essentially derived from the three valleys of the anterior 

 Rhine, the middle Rhine, and the xilbula, the two latter of 

 which unite in the Domleschg, and again join themselves, 

 above Coire, to that of the anterior Rhine. Further down, 

 the valley of Praettigau, and especially the great valley of 

 Montafun, on the I'ight bank, furnish to this basin a contin- 

 gent of rocks proportionally very considerable. 



A little way from its origin, the basin of the Rhine pre- 

 sents a very remarkable bifurcation ; the erratic formation 

 diverges not only by the transverse valley which the Rhine 

 follows from Meyenfield and Luciensteig, but likewise by the 

 lake of Wallenstadt and the valley of Gaster, where it en- 

 counters blocks of the valley of Limmat, in the neighbour- 

 hood of Wesen and Schaennis. There it is gradually pushed 

 back by the more powerful erratic formation of the Linth ; 



