M. Andi'e cle Luc on the Glaciers of (he Alps. 19 



In order to assure oui'Selves of the effect of a glacier upon 

 its bed, it would be necessary to creep beneath it ; for a glacier, 

 when retu-ing, leaves such masses of stones upon the ground, 

 that it is impossible to discover what goes on beneath ; it is 

 supposed that a glacier, by rolling stones under it, may have 

 the effect of rubbing down the rocks. 



Our author thus conjectm-es, that the polished rock of St 

 Bernard has been polished by an ancient glacier. This polish- 

 ed rock is found at the summit of a mountain very remote from 

 glaciers. It consists of the walls of a fissure which penetrate 

 into the mountain at a great angle, and which consequently 

 have never been at the surface ; their polish is owing to a 

 quartz coating, in which can be detected the striae of rock-crys- 

 tal, or rather this is the effect of a strong friction in the same 

 direction, by the rubbing of one of the Avails upon the other. 



But I have it in my power to refer to polished rocks where 

 certainly a glacier never passed. M. Thu-ria,* speaking of the 

 transported matter AAhich fills the depressions and fissures of the 

 ground in the Flaute-Marne, says, that this matter is composed 

 of the debris of surface rocks, and these debris fill depressions 

 as well as cavities and rents ; now, the bottom of the de- 

 pressions which these debris fill, and likewise the walls of the 

 cavities and rents which conceal them, have a smooth and 

 polished surface, in every respect resembling the caves in the 

 Jura Mountains, which contain portions of diluvial eax'th along 

 with the animal remains of that epoch. 



Such is the cause of the polish on the rocks of .Jura in tiie 

 neighbourhood of Neuchatel and Bienne, on which M. Agassiz 

 rests his case so strongly. This cause is as remote as the di- 

 luvian era, when immense currents carried along great masses 

 of debris. This is likewise the opinion of Professor Studer of 

 Berne. 



The object of the memoir which I addressed to the Geolo- 

 gical Society of France, is to shew that the phenomenon of 

 rolled or transp(jrtcd blocks of stone is not confined to those 

 which have been observed at great intervals in the central 

 chain of the Alps, but that they are found as far as the base 



* Tliu-ria sur lo Miucrai dc For dela HaBtc-Marno. {Aimahf des Miiu-s, 

 '■i*' sera- ; t. xv. Paris, l}jr.(.>. 



