472 



EEVIEWS. 



Carte Geologique du Dejpartement de la Loire-Inferieure. Par M, 

 Cailliaud. Leipzig : J. Rotliscliild. 



It is Tvith mncli pleasure tLat we notice so excellent a local map as the . 

 one before us by M. Cailliaud ; tlie result of fifteen years of excursions, 

 during which period that gentleman has paid close attention to every im- 

 portant excavation that has been made in the department of tlie Loire- 

 Inferieure. The authoritative specimens, moreover, upon which he has 

 founded the stratigraphical divisions of his map, amounting to upwards of 

 four thousand, have been placed in the museum of Nantes, where they 

 are not only a standing proof of the value of M. Cailliaud's labours but 

 can also be usefully consulted by all who have any interest in the geology, 

 the arts, manufactures, and agriculture of the district. 



The geological constitution of the department affords two well-marked 

 divisions. In the northern part more than a third of its extent belongs 

 chiefly to the transition rocks ; the line of demarcation being east and west, 

 following the Loire, Ingrande, to beyond Ancenis, Ligne, Blain, and Dreffear. 

 The opposite portion, containing two-thirds of the area, is divided centrally 

 by the valley of the Loire from east to west. Its chief geological features 

 are primitive formations, or azoic crystalline rocks. No traces of volcanic 

 rocks are met with. The rock divisions recognized begin with the lowest 

 or Primary period ; these are gneiss, crystalline micaceous schist, and 

 granite, into which the former often pass by insensible gradations. In the 

 quarries of Saint-Gervais the granite is seen partly stratified ; and protogen 

 granite is observed at Sorinieres. The ordinary direction of the granite 

 and gneiss is N.W. and S.E. The map shows 36 granitic regions ; 16 of 

 eurite, more or less porphyritic ; 20 of amphibolite ; 59 serpentine ; several 

 traps ; 25 of Lydian quartz ; 10 of diorite and eclogite, the latter con- 

 taining garnets. M. Lory has described, in the Transactions by the Erench 

 Geological Society the occurrence at La Paquelais, near Monitoir, of 

 a leptynoid and granitoid gneiss in regularly bedded and almost vertical 

 strata. 



Next are noticed the rocks of the "Periode Phylladienne." The Silurian 

 rocks occupy a sixth of the area of the northern part. Numerous open 

 mines of hydroxide of iron are worked. The prevailing direction of the 

 beds in the west of the department is W. 10° to N.E. 15°, 10° to 15° S., 

 plunging 45° to 50° to the S.E. A band of silurian quartzite is found to- 

 wards the north, and a limestone-marble is met with atD'Erbray and Saint 

 Julien de Vouvantes, belonging to the Lower Devonian. 



The LTpper Silurian, in its vicinity, is said to contain masses of crystalline 

 marble distinct from the Devonian limestone, and bearing fossils character- 

 istic of the third Silurian fauna of Barrande. Other Devonian beds occur 

 at Ingrande, Ligne, and the banks of the Loire, etc. Half a kilometre 

 N.E. of Brulis the schist-zone envelopes a second calcareous marble; and 

 at Ecochere the grey or pinkish rock is often mingled with beds of greenish 

 schist. This deposit is considered to be middle Devonian by Dr. Bureau, 

 who has found in it some good fossils characteristic of a higher level than 

 that of Bruhs. 



North of Ancenis Upper Devonian rocks occur; and north, again, of 

 these beds is the argillaceous sandstone known as grauwacke, with quart- 

 zose pudding-stones and clay nodules. The superficial portion of these 

 rocks shows vestiges of anthracitic schists and impressions of plants. 

 Anthracitic deposits occur at Done in Anjou, at Effeterie, and Malabrit ; 



