68 M. Ch. Martins on the 



the strice engraven by glaciers. This fact may be verified at 

 the foot of those in the valley of Grindelvvald. At 300 metres 

 from the escarpment, the torrents which issue from it carry 

 along only rounded pebbles, but they are smooth and com- 

 pletely deprived of striae. I assured myself of this in the 

 most positive manner. Indeed, M. Edward Collomb solved 

 the question in an experimental manner. lie took pebbles 

 striated by the glaciers, and placed them along with sand and 

 water in a horizontal cylinder, which was turned round only 

 fifteen times in the minute. At the end of twenty hours, all 

 the stria) had disappeared. Accordingly, we shall seek in 

 vain for them on pebbles rolled along by the most violent 

 torrents, or on banks where the flux and reflux of the sea 

 washes continually, driving them to the shore, and again 

 sweeping them back towards the deep. 



After these details, we hope that the proofs which we ad- 

 duce to demonstrate the ancient extension of existing glaciers, 

 will be at least sufiiciently intelligible. We have purposely 

 omitted all that had not a direct application to the study of 

 this great phenomenon. The method we adopt to prove this 

 ancient extension, is at once the most simple and the most 

 certain that can be followed in geology. We shall traverse 

 the countries which surround the Alps, and inquire whether 

 they present indubitable traces of the action of glaciers. If 

 we everywhere find these traces as numerous and as evident, 

 as in the neighbourhood of existing glaciers, we shall be in- 

 evitably led to admit, that formerly they descended into the 

 plain, and filled the interval which separates the Alps from 

 the Jura. The ancient extension of glaciers will be demon- 

 strated, without it being in our power to give an account of 

 the meteorological perturbations which accompanied them ; 

 for, in a study which dates only a few years back, we cannot 

 flatter ourselves with having brought together a sufficient 

 number of facts to enable us to ascend to the cause which 

 produced this phenomenon. We may merely affirm, that this 

 prodigious development of the seas of ice would be impossible 

 in the existing climatic conditions, and that it necessarily 

 supposes a notable depression in the temperature, and, con- 

 sequently, a diff'erent climate from what now prevails in 

 Europe, 



