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'DYNAMICAL GEOLOGY. 



The forms of veins and their courses are greatly varied by faults. 

 Some examples are represented in figures on pages 109 and 111, and 

 these figures may be taken either as of natural size or as represent- 

 ing faulted veins a thousand times as large. But faults may divide 

 veins not merely into parts that are little displaced, but into portions 

 that are shoved hundreds or thousands of feet to one side or the 

 other, above or below, to the immense perplexity of the miner. Even 



Fig. 1128. Fig. 1129. 



small faultings may divide a vein into isolated portions that have no 

 apparent connection whatever. The annexed figures illustrate one 

 method ; the fissure being sinuous, a slight movement in the direction 

 of the vein has brought the projecting part of the two sides together, 

 and doubled the width of the rest. In Fig. 1129, from De la Beche, 

 representing nature most correctly, a is the line of a somewhat sinu- 

 ous fissure, b, the result of a fault to the right along this line, and c, 

 the result of a fault to the left. In rocks that are nearly vertical in 

 dip, the subdivisions of the vein made by faulting may be vertical, as 

 is illustrated by each of the above figures, if it be regarded as repre- 

 senting a horizontal surface. 



In the case of faulted veins, the inclination of the plane of the fault 

 to a vertical plane is called by miners its hade ; and it is so common 

 to find the hade or pitch toward the down-throw side, that when it is 

 not so the fault is called a reversed fault. The down-throw is usually 

 on the same side (referred to the points of the compass) in all the 

 veins of a region, as if all had been produced by the same subterra- 

 nean movement. 



In the making of fissures, portions have often been separated from 

 the walls ; such a mass in a vein is called by miners a horse, while 

 many of them may make it a brecciated vein. In some cases beds of 

 rock have been crushed into large and small fragments for a great 

 width ; and the vein-material has filled up the spaces between them, 

 so that the whole looks like an enormously coarse breccia. 



3. Structure. — Veins (1) may be simple in structure, that is, have 

 the material, not divided into layers, but as one mass from side to side, 

 with the ore or metal, if they contain any, disseminated through the 

 mass; or, (2) they may be banded, that is, have the materials ar- 



