220 LOCALITIES FOR GRANITE. 



Granite is sometimes supposed to be formed at successive periods 

 in a mountain chain, and in the ThuringerWald, Credner defines three 

 granites having such relations to each other. 



Contact Metamorphism. In the island of Skye, where the granite 

 comes in contact with limestone, the latter rock is changed into a 

 crystalline marble. Many minerals are developed in the limestone 

 near the contact, but the most common are garnet, vesuvian, epidote, 

 spinelle, hornblende, augite, and mica. Clay slate is modified in 

 Cornwall, between Constantino and Penryn, into mica schist and 

 gneissose rock, where it comes into contact with granite, with the 

 development of tourmaline, chiastolite, and other minerals. Similar 

 phenomena are seen in the Pyrenees, Saxony, Brittany, and most of 

 the granitic localities. Hornstone is sometimes produced at the con- 

 tact by a process of silicification of very fine-grained sandy rocks, 

 though ordinary sandstones become altered into quartzites. 



Modes of Occurrence of Granite. In the south of Russia there is 

 an elliptical granitic area of nearly 4000 square miles. It reaches from 

 Owracz in Volhynia in a S.E. direction to the neighbourhood of Tagan- 

 rog, and in a westerly direction stretches nearly to Brody in Galicia. 

 In Saxony, between Gorlitz and the Georgenthal in Bohemia, there 

 is an area of forty square miles of granite. Between the Tagus and 

 Guadiana there is a granite plateau. In those cases the granite is 

 assumed to be horizontal. And many instances are quoted by Zirkel 

 in which granite is an overlying rock, and follows the undulations of 

 slates and schists on which it rests. Among these are the well-known 

 instance on the banks of the Irtish in Siberia, originally described by 

 Von Humboldt ; Marhallac's examples in the islands of Milhau in the 

 the Cote du Nord in France ; and others in the Harz and the Erzge- 

 birge. But granite more frequently occurs in consecutive masses like 

 chains of islands which have been exposed by denudation, and are 

 elevated with the great folds of the earth's crust. 



The principal granitic districts in Europe comprise : 



FRANCE. Eastern part of the Vosges, much of the high land of the 

 Auvergne, the district between JS T antes and Parthenay, the Pyrenees, 

 and Brittany. 



GERMANY and AUSTRIA. West of the Schwarzwald, in the Oden- 

 wald, south of the Thuringerwald, in the Harz, much of the Eich- 

 telgebirge, several areas in the Erzgeberge, Oberlausitz, in Bohemia, 

 the Biesengebirge, the Sudetic Alps, the highest peaks of the Tatra 

 in the Carpathians, the Bohmerwald. 



SWITZERLAND and ITALY. Mount Blanc, St. Gothard, &c., Velte- 

 line Alps, Trientine Alps, &c., Corsica and Elba. 



SPAIN. N.W. province of Galicia, the Sommo-Sierra, the Gua- 

 darrama Mountains, the Sierra Morena. 



SCANDINAVIA. A large part of the peninsula. 



RUSSIA. East side of the Ural, and a large area in the south. 



Varieties of Granite in the United States. The granites of 

 North America are classed by Clarence King into eruptive and meta- 

 morphic, and he groups the eruptive series into four divisions. The 



