M. Renoir on the Glaciers of the Vosges. 295 



planation respecting the character and length of the striae 

 which have been spoken of above. These short and fine striae, 

 he said, have been produced by insulated angular stones harder 

 than those on which they have left their marks, in consequence 

 of the double action of friction and pressure. The mamellatcd 

 parts (^parties mamelonnees), on the contrary, would result 

 from the friction of the glacier itself, moving on its under 

 side. I may add, continued M. Leblanc, that M. Fergeaud, 

 Professor of Physics to the Faculty of Strasburg, has disco- 

 vered analogous phenomena in the mountains of the Black 

 Forest in those of the Vosges and Pyrenees, which he has 

 lately examined, and which he also endeavours to explain by 

 the theory of glaciers. 



M. Voltz has remarked, in deposits of granular iron-ore, 

 striae, which were terminated by a grain of that substance. 



M. de Roys said, that in the chain of the Alpines, between 

 St Remy and Aries, he has noticed a great number of these 

 polished surfaces looking as if overspread with a varnish, and 

 presenting a few striae. These hills do not rise beyond 100 

 or 150 metres above the Mediterranean, and he does not think 

 that this effect can be attributed to glaciers.* 



On the Origin of Granite^ and on the application of the Hutto- 

 nian Theory to the present state of Geology. By M. B. Stu- 

 DER of Berne. In a Letter to Professor Bronn.t 



The letter you sent me at the close of last year, contains so 

 much that is calculated to excite, and touches upon so many 

 important geological inquiries, that, throughout the whole 

 winter, I have been anticipating much pleasure in the prospect 

 of answering it. Since, however, my approaching journey to 

 Italy has been determined upon, I have been so much occu- 

 pied, that I have been unable to command time for the calm 



* Bulletin de la Societd Geologique de France, for Feb. 1840. 

 t From Neues Jahrbuch fiir Mineralogie, &c. Jahrgang 1840. 



