Let us now turn to the foliation of the metamorphic schists, a subject which has been much less attended to. As in the case of cleavage-laminae, the folia preserve over very large areas a uniform strike: thus Humboldt found for a distance of 300 miles in Venezuela, and indeed over a much larger space, gneiss, granite, mica, and clay-slate, striking very uniformly N.E. and S.W., and dipping at an angle of between 60 and 70 degrees to N.W. (“Personal Narrative” volume 6 page 59 et seq.); it would even appear from the facts given in this chapter, that the metamorphic rocks throughout the north-eastern part of South America are generally foliated within two points of N.E. and S.W. Over the eastern parts of Banda Oriental, the foliation strikes with a high inclination, very uniformly N.N.E. to S.S.W., and over the western parts, in a W. by N. and E. by S. line. For a space of 300 miles on the shores of the Chonos and Chiloe Islands, we have seen that the foliation seldom deviates more than a point of the compass from a N. 19 degrees W. and S. 19 degrees E. strike. As in the case of cleavage, the angle of the dip in foliated rocks is generally high but variable, and alternates from one side of the line of strike to the other side, sometimes being vertical: in the Northern Chonos Islands, however, the folia are inclined almost always to the west; in nearly the same manner, the cleavage-laminae in Southern Tierra del Fuego certainly dip much more frequently to S.S.W. than to the opposite point. In Eastern Banda Oriental, in parts of Brazil, and in some other districts, the foliation runs in the same direction with the mountain-ranges and adjoining coast-lines: amongst the Chonos Islands, however, this coincidence fails, and I have given my reasons for suspecting that one granitic axis has burst through and tilted the already inclined folia of mica-schist: in the case of cleavage, the coincidence between its strike and that of the main stratification seems sometimes to fail. (Cases are given by Mr. Jukes in his “Geology of Newfoundland” page 130.) Foliation and cleavage resemble each other in the planes winding round concretions, and in becoming tortuous where veins of quartz abound. (I have seen in Brazil and Chile concretions thus enfolded by foliated gneiss; and Macculloch “Highlands” volume 1 page 64, has described a similar case. For analogous cases in clay-slate, see Professor Henslow’s Memoir in “Cambridge Philosophical Transactions” volume 1 page 379, and Macculloch’s “Classification of Rocks” page 351. With respect to both foliation and cleavage becoming tortuous where quartz-veins abound, I have seen instances near Monte Video, at Concepcion, and in the Chonos Islands. See also Mr. Greenough’s “Critical Examination” page 78.) On the flanks of the mountains both in Tierra del Fuego and in other countries, I have observed that the cleavage-planes frequently dip at a high angle