THE HORNBLENDIC SCHISTS. 205 



seeius to increase as the schistosity of the rock becomes inon; marked 

 In the less schistose specimens the amphibole has been hirgely chang-ed 

 into chlorite and epidote, while calcite in large qiiantity satnrates the rocks. 

 In some of the chlorite plates are series of fine rutile needles, cutting- one 

 another at angles of 60°, as though the chlorite had originally been a 

 biotite. Moreover, there are occasionally scattered through the chlorite 

 yellowish-brown flakes with the cleavage, pleochroisin, and extinction of 

 this mica. Leucoxene, sphene, magnetite, limonite, and hematite are met 

 with in most sections, and fairly large prisms of a bluish-brown tourmaline 

 are discovered in a few. 



Dynamic effects are seen in a number of the least altered schists, but 

 they are largely obscured by the gi-eat quantity of decomposition products 

 present in all of them. Fractured plagioclases are sometimes so abundant 

 that the rocks look like tuffs. 



From the microscopical features of the rocks and from the strong 

 analogy they bear to the northern greenstone-schists and the schistose Inisic 

 dikes that intrude them, we may safely conclude that, like the northern 

 rocks, they are squeezed eruptives— lavas and intrusive masses in the case 

 of the unbanded varieties, and tuffs in the case of the banded kinds. 



The types of green schists described are the predominant ones in the 

 Southern Complex. There are, however, a great many other interesting 

 varieties met with, all of which may be traced, under the microscope, into 

 the types just described. Certain epidotic varieties deserve mention for the 

 great quantities of this mineral they contain. They are composed very 

 largely of dark-gi-een, imperfect hornblende crystals, in a matted mass of 

 smaller chloritizecl flakes of the same mineral, and large and small areas 

 of an almost colorless epidote and saussurite in plates and grains. Besides 

 these minerals, brown hornblende in plates, small grains of quartz, little 

 areas of feldspar mosaic, and some magnetite are always ]n-esent, but of 

 these minerals only the biotite is ever in large quantit}-. The biotite 

 seems to be more abundant near the feldspar areas than elsewhere, and the 

 epidote appears to replace this mineral. 



Another type that must be briefly refen-ed to is intermediate in its 

 characteristics between the greenstone-schists and the amphibole-schists to 



