REPORT ON MINERAL VEINS. 17 



tion ; 3. The contemporaneous veins, which might more aptly 

 be termed veins of segregation. 



Here I might close this Report, which is already much too 

 tedious, were it not that I may be expected to notice briefly 

 some of the facts adduced by the advocates of the respective 

 theories, and, by comparing them, show how far they are enti- 

 tled to be considered as objections on one side, or as proofs 

 on the other, with the confidence which has been assigned to 

 them. 



Werner and Hutton agree in allowing that rents took place 

 subsequently to the consolidation of the rocks, or at the time of 

 their consolidation. They differ as to the cause of the rents : 

 Werner ascribes it to subsidence, or to sinking and shrinking 

 of the solid materials of our globe ; Hutton, to violent upheaving 

 of matter from below, breaking up the superinjacent strata. 



Either of these causes seems adequate to the effect, and in 

 either case corresponding strata might be found having different 

 levels of position on opposite sides of the fissure, as is constantly 

 the case. This by miners in the North of England is called the 

 throw of the vein ; and it is clear that one side may as well be 

 thrown up as the other thrown down. Mr. Fox and Dr. Boase 

 urge the great irregularity of the width of veins, the difficulty 

 of supposing the sides to be supported, and some other objec- 

 tions to the hypothesis of open fissures. Irregularity of width 

 is but a comparative term ; and taking into consideration the 

 immense extent of their dimensions in length and depth, it 

 amounts in my opinion to but little. 



The other objections are in a great degree anticipated and 

 answered by Werner ; and, after all, difficulties can hardly be 

 urged against the positive testimony of some veins having been 

 open, which is afforded by the substances found in them, such 

 as rolled pebbles, petrifactions, &c. 



The parallelism of veins of one formation is insisted upon by 

 Werner as a proof of his view of the subject ; and I confess that 

 there appears to me to be considerable difficulty in explaining 

 this, on the supposition that fissures were caused by a mass 

 protruded upwards through strata already foi'med. From such 

 a cause one should expect not to have a number of cracks pa- 

 rallel to each other, but rather to see them radiating from the 

 centre of the greatest disturbance. In the metalhferous veins 

 we may certainly observe this parallelism to a great extent. 

 Mr. Carne has beautifully illustrated this in Cornwall, and has 

 shown how the productive veins generally have an east and 

 west course ; how, as they differ in their contents, they diff'er 

 also in their direction, each class being, however, parallel in 



18^3. c 



