during the Year 1828. 411 



cific gravity is also less in those varieties which are produced 

 by decomposition. The great proof, that the specific gravity 

 depends on the quantity of vacant space in minerals, is, that 

 when all the varieties are reduced to powder they weigh 

 alike. 



Among the notices on Geology are the following: — M.Roset 

 has been continuing the researches of Dr. Fitton, in the Bas 

 Boulonnais, and confirms the English geologist's theory, that 

 the strata of this district are exactly similar to those of the 

 opposite county in England, both in composition and position. 

 To these researches M. Roset has added many new details 

 and maps. — A bed of manganese, situated at Romaneche, 

 near Macon, has attracted the attention of geologists, and 

 some (among whom is the celebrated Dolomieu) have thought 

 it to be a vein, and others have supposed it to be a heap or 

 mass placed upon the granite. According to the recent ob- 

 servations of M. Bonnard, it appears to accord with each 

 opinion. At Romaneche, where it is worked, it certainly lies 

 in a heap above the granite ; but to the south of this village, 

 and in the same direction, it forms a true vein, which traverses 

 the granite, and in every respect resembles the heap in sub- 

 stance : a circumstance which M. Bonnard looks on as likely 

 to substantiate the theory, that certain formations are caused 

 by subterranean overflowings. The* same author conjectured 

 that the deposits of manganese at Dordogne were similarly 

 situated ; a supposition which has been confirmed by M. Du- 

 fresnoy, who, with his companion M. Elie de Beaumont, is 

 preparing a geological map of France. 



Several caverns, which were supposed to be destitute of 

 fossils, have, since Dr. Buckland's instructions on the manner 

 of finding them, produced a number of very interesting remains. 

 M. Delanoue has just found a new instance of their constant 

 occurrence in subterranean caves, in the grotto of Miremont, 

 in the Dordogne department. This grotto appears to have 

 been hollowed out in an intermediate formation, between chalk 

 and Jura limestone. The-galleries are 2000 paces long, and 

 end in a multitude of low, narrow ramifications, where the 

 bones are deposited. They are enveloped in red clay, and are 

 principally those of bears. Some pits, dug from two to four 

 hundred paces from the mouth, exposed different layers of 

 marl, which appeared to be more recent than the red clay. 

 In these were found some broken pieces of pottery, similar to 

 those contained in the ruins and alluvial earth of the neigh- 

 bourhood, and which are supposed to be prior to the intro- 

 duction of Roman arts into France. 



E E 2 .^i':.jr^ 



