Dr. Mac Culloch on Mineral Veins. 195 



• These are the leading objections to the general hypothesis, 

 and they are unanswerable. The few real arguments from facts 

 which have been adduced in support of it, are of small value, 

 and will require very little discussion. 



If it be conceded, as is the fact, that many of the substances 

 found in veins are the produce of watery solution, there are 

 many others which , as far as we yet know, cannot be produced 

 in this manner. Not to enumerate all these, it is sufficient to 

 notice in general, the greater number of the metallic minerals. 

 It has been argued, that the minerals of veins are deposited in 

 layers parallel to their sides, precisely as ought to have hap- 

 pened on this hypothesis. To this it is easily answerfed, that 

 the fact is not so, except occasionally ; as they are frequently 

 congregated in irregular lumps, or dispersed among the other 

 materials, or wanting for considerable spaces, or found lining 

 the insides of cavities. Neither of these occurrences ought to 

 be found, according to the hypothesis ; and, more particularly, 

 there could be no cavities on such a system of deposition from 

 above. In such a case, also, the layers of minerals ought rather 

 to be parallel to the horizon than to the walls of the vein. The 

 argument derived from the presence of rounded materials in 

 veins is worthless, because the fact itself is extremely rare. It 

 is an exception instead of a rule, and may be admitted without 

 involving the whole hypothesis. 



With respect now to the other theory, v/hich presumes that 

 the contents of mineral veins have been injected from below, as 

 those of granite and trap veins have been, the difficulties are 

 assuredly not less, if they are not even greater. The arguments 

 for it rest partly on this very analogy ; partly on real or imagi- 

 nary chemical facts relating to the production of minerals by 

 fusion ; partly on some mechanical appearances ; and partly on 

 the principle of dilemma. If it be really a case of dilemma, the 

 one horn appears as fatal as the other, and there can be no 

 theory of mineral veins. 



The argument from the analogy of trap and granite veins is 

 exactly one of those superficial resemblances, consisting in 

 words rather than things, which it is painful to find in the writ- 



