V E I 



[453 ] 



V E N 



sive plain countries are totally de- 

 stitute of them, there are few 

 mountainous districts in which 

 they are not abundantly found. 

 It has been very generally ob- 

 served that the character of metal- 

 liferous veins changes with the 

 structure of the rock through 

 which they pass. If the direction 

 of a vein approaches to a vertical 

 plane, it is called a rake vein, if to 

 the horizontal, a pipe or flat vein. 



The depth to which the metallic 

 veins descend is not known, all 

 large veins continuing beyond the 

 reach of the deepest mine. They 

 frequently contain totally different 

 ores at different depths. 



Veins vary in width from less 

 than an inch to thirty feet and 

 upwards ; sometimes the same vein 

 at one part contracting, so as to 

 be almost lost, and then expanding 

 to an immense width. 



Werner supposed that veins had 

 become filled by matter descending 

 into them from above, in a state of 

 aqueous solution : Hutton, on the 

 other hand, imagined that their con- 

 tents were injected from below, in a 

 state of igneous fusion. A third 

 hypothesis refers the filling of veins 

 to a process of sublimation from 

 subjacent matters of intensely 

 heated mineral matter, into aper- 

 tures and fissures of the superin- 

 cumbent rocks. A fourth hypo- 

 thesis attributes these metallic 

 collections to segregation, or in- 

 filtration. Buckland says, " What- 

 ever may have been the means 

 whereby veins were charged with 

 their precious contents ; whether 

 segregation or sublimation were 

 the exclusive method by which the 

 metals were accumulated ; or, 

 whether each of the supposed 

 causes may have operated simul- 

 taneously or consecutively in their 

 production ; the existence of these 

 veins remains a fact of the highest 

 importance to the human race : 



and although the disturbances, and 

 other processes in which they 

 originated, may have taken place 

 at periods long antecedent to the 

 creation of our species, we may 

 reasonably infer, that a provision 

 for the comfort and convenience of 

 the last, and most perfect creatures 

 He was about to place upon its 

 surface, was in the providential 

 contemplation of the Creator, in 

 His primary disposal of the phy- 

 sical forces, which have caused 

 some of the earliest and most 

 violent perturbations of the globe.' ' 



YEIN-STONE. 1. The earthy, stony, 

 saline, or combustible substance, 

 which contains the ore, or is 

 mingled with it, without being 

 chemically combined, is called the 

 gangue, or vein-stone. 

 2. Vein- stones are the different 

 stony substances with which the 

 ore is intermixed, and which as a 

 whole constitute the vein. Werner 

 was of opinion that in the same 

 vein the parts of the vein-stone 

 nearest to the Saalbande are the 

 oldest, those in the middle the 

 most modern, and the intermediate 

 parts of a middle age. 



YENERICA'RDIA. A genus of equi- 

 valved, inequilateral, marine, ob- 

 long bivalves; ribbed longitudinally 

 on the outside; two thick hinge- 

 teeth disposed obliquely, and in 

 the same direction : muscular im- 

 pressions two. Venericardia3 are 

 found recent and fossil. The 

 recent are met -with at depths 

 of the ocean varying to fifty 

 fathoms, in mud and sands. Fossil 

 venericardia3 are found in the se- 

 condary and tertiary formations. 



VE'NTEICLE. (from ventriculus, Lat.) 

 A chamber or cavity ; the stomach. 

 A term applied to different cavities 

 of the body. The heart contains 

 two chambers distinguished as the 

 right and left ventricles, as well as 

 two others, termed auricles. Cer- 



