and their Connexion with Volcanos. STl 



of waters, such as that by which the contiguous rocks may have 

 been affected, as to the more gradual working of the stream, 

 which at present traverses it in its way from the upper to the 

 lower longitudinal valley just mentioned. The extreme nar- 

 rowness of the glen itself, which in some places does not exceed 

 150 feet, and the greater abruptness of the rocks by which it is 

 flanked, than of those found elsewhere in the same neighbour- 

 hood, are facts, which tend to separate its origin from that which 

 we should assign to the generality of the contiguous valleys, and 

 which speak strongly in behalf of our considering it as occasion- 

 ed by some sudden violence. 



The nature of the rocks themselves also favours the same con- 

 clusion. High up on either side of the valley, they are com- 

 posed of granite, but towards its bottom, wherever the nature 

 of the substratum is not concealed by the calc-sinter which the 

 springs at the present time deposit, they are found to consist of 

 breccia, made up of fragments of the granitic rock, cemented by 

 infiltrations of siliceous or calcareous matter. As this breccia 

 is not found elsewhere, we have strong reason for supposing the 

 material of which it is made up, to have been torn from the 

 granitic rocks adjacent, at the very time when this fissure was 

 occasioned. The alteration observed in the nature of the 

 cementing ingredients, is consistent with what we observe in hot 

 springs of unquestionable volcanic origin, in which it is found, 

 that silex is held in solution when the action is recent and ener- 

 getic, but gradually gives place to calcareous impregnations as 

 the latter becomes more languid. 



Still more remarkable is the gorge out of which gushes the 

 hot spring of Pfeffers in the Grisons, a fissure, says Ebel, 

 from 400 to 664* feet in depth, so perpendicular, that the pro- 

 visions required for the inmates of the bath are lowered from 

 ropes attaclied to the summit of the cliff, and so narrow, that 

 the rocks in some places touch overhead, and nowhere perhaps 

 are more than thirty feet apart. M. Ebel remarks, with reason, 

 that such a phenomenon cannot be attributed to the river which 

 now flows through the glen, but accounts for it by the action of 

 some larger body of water that once swept over the country, — a 

 position in my judgment just as untenable. The only possible 

 explanation of such a phenomenon is to be found in some convul- 



