198 Dr. Mac CuUoch on Mineral Veins. 



aqueous theory, no close veins or deposits of minerals, sur- 

 rounded on all sides by rock, could exist. But it is obvious 

 that these are equally impossible, on the other view of a cause. 

 Where there is no access for a watery solution, there is none 

 for an igneous fluid. To make use here, as has been done, 

 of a theory of igneous secretion, such as been applied to the 

 nodules of trap, is to adopt a scheme which is perfectly gratui- 

 tous, and to reject one the existence of which is proved. If 

 mineral veins have, in any case, been filled by a secretion from 

 the including rocks, there can be no choice between a process 

 which is actually proved to exist in nature, and one which, not 

 only has not been observed, but which is supported by no che- 

 mical analogy. 



It has also been said, that the solidity or fulness of mineral 

 veins could only have happened from igneous injection ; as the 

 abstraction of ihc water after deposition, must have left cavities 

 or vacuities of some kind. With no small want of reflection, 

 it has also been said that cavities could only have been formed 

 in them on the igneous hypothesis, from the disengagement of 

 elastic fluids. These, it is plain, are conflicting statements ; 

 as, without a charge of captiousness, may be fairly urged. 

 The fact, such as it is, is quite as explicable on the one hypo- 

 thesis as on the other, and is alike worthless to both. The 

 want of marks of gradual and regular deposition, is a negative 

 argument, which, if it proves one hypothesis to be wrong, does 

 not render the other right ; and, with respect to the existence 

 of fragments already mentioned, the state of these is assuredly 

 calculated to prove any thing but that they have been sup- 

 ported and involved by an ignited fluid. 



Such are the objections to an hypothesis, which, however 

 it might be deemed a necessary part of the general theory to 

 ■which it belongs ; and, however we may respect the talents of 

 its author and supporter, cannot command a moment's atten- 

 tion, unless it shall hereafter be most materially modified by 

 new views and new discoveries. Thus modified, it must indeed 

 disappear ; but its downfal does not involve that of the theory 



