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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1916 Excerpt:...toward the left (a'), and the leaflets below have been lengthened an the right (b'). (About M natural size.) 216----Deformed impression of d 'nto thm 21) or they may ses being schistoslty ' ' ) the deforma 1 ' b distorted llshed by roc tituents in thin accomp ' Schists sometimes have a wavy streaking of their cons ' cross-bedding. lines that may _be mistaken for---fossil frond deformed by shearing. The midribs of the leaflets the leaflets above have been shortened and d rotated toward (Figs. 215, 216), and unfortunately only a little shearing is enough to deprive them' of their value so far as this depends upon the recognition of species. In the deformation of any lithologic feature, all stages may exist between very slight change and very great change (212), and in rocks that have been intensely metamorphosed such original features may have been obliterated. Thus, curious though it may seem, the distinction between sheared quartz veins and sheared quartzite pebbles may be almost impossible in cases of extreme metamorphism. Lithologic structures in igneous rocks may likewise be deformed, but here one must be careful not to confuse phenomena due to magmatic flow with those which are of truly metamorphic nature (214). If possible it is good policy for the beginner to postpone studying highly metamorphosed rocks in the field until he has first become familiar with the primary characters of sediments and igneous rocks. 212. Degrees of Dynamic Metamorphism in Clastic Sedimentary Rocks.--Like contact metamorphism, dynamic metamorphism exhibits various degrees of intensity (121). To be sure there is great complexity in the latter type of alteration on account of many factors, such as the composition and texture of the rock, yet certain stages can...