GNEISS IN AMERICA. 395 



the lower mountains of Caracas, in Orinoco, Brazil, New Spain. It 

 is occasionally auriferous, and contains micaceous crystalline limestone. 

 The most considerable masses of mica slate mentioned by this traveller 

 are those of the Cordillera of the shore of Venezuela. This rock in 

 the Andes is less rare on the north than on the south of the Equator. 

 Nowhere, perhaps, is the total suppression of mica slate more frequent 

 than in the Cordilleras of Mexico and South America. 



The eastern primary range of North America passes through the 

 United States from the St. Lawrence to the Mississippi in a direction 

 nearly parallel to the coast, and at first 100 miles distant from it. 



The prevailing and characteristic rock is a syenitic gneiss, in which 

 the divisional planes are obscure, and frequently evanescent, when 

 the rock is undistinguishable from the syenite which forms part of 

 this great metamorphic group. Gneiss retains in general its place 

 next the granite, which, however, is of small extent ; it is often suc- 

 ceeded by hornblendic, micaceous, and talcose schist, and granular, 

 sometimes dolomitic limestone, seldom pure enough for fine statuary. 

 It is traversed by granite veins at Haddam in Connecticut. 



This is the principal metalliferous band in the Eastern UnitedStates, 

 yielding magnetic iron ore in veins and beds, near Lake Champlain, 

 in New York, New Jersey, Pennsylvania, and Maryland ; on the 

 southern side of Lake Superior, in the vicinity of Montreal, in Wis- 

 consin, in the Iron Mountain and Pilot Knob in Missouri, and in 

 Arkansas. Copper ore occurs in Lake Huron and on the northern 

 shore of Lake Superior. Lead ore lies in these rocks in northern 

 New York ; lead and copper in Pennsylvania ; zinc or red oxide, 

 mixed with franklinite, occurs in New Jersey ; phosphate of lime 

 has been found in New York and New Jersey ; kaolin marble, build- 

 ing stone, firestones, hones, steatite, plumbago, and many fine 

 crystallised minerals, as apatite, zircon, spinelle, sphene, augite 

 tourmaline, may be added to this list. 



The range of the rocks is from the high country north of the St. 

 Lawrence, westward to the sources of the Mississippi, and southward 

 along the elevated parts of Maine, New Hampshire, New York, New 

 Jersey, Pennsylvania, Maryland, Virginia, and North Carolina, to 

 Alabama, with isolated belts in Missouri, Arkansas, and Texas. 



Gneiss of North America. Gneiss varies in mineral composition, 

 and presents analogies towards different igneous rocks. At the north 

 end of the Lake range in Nevada, the felspar is almost entirely 

 triclinic, with a little orthoclase. There are also present biotite, quartz, 

 and green hornblende, so that it corresponds to quartz-mica-diorite, in 

 the same way that common mica gneiss corresponds to granite, and 

 hornblende gneiss corresponds to quartz syenite. The quantity of 

 prisms of apatite is enormous in this rock, as in all gneisses which 

 abound in hornblende. In Clover Canon many varieties of gneiss 

 occur, some representing the diorite gneiss, but with the titanite in 

 greyish yellow sharp sections ; other Clover Canon gneisses contain 

 inclusions of liquid carbonic acid. In Europe, liquid carbonic acid is 

 found in quartz in the granitic gneiss of the St. Gothard, and grey 



