i'4 THIRD REPORT 1833. 



tions, which deposited the substances with which they were 

 charged in the veins, or by the process of subhmation from 

 below. 



The second theory allows that veins were formed subse- 

 quently to the consolidation of the rocks ; but the cause prin- 

 cipally assigned for such fissures is the violence done to the 

 strata by the elevation or upheaving of other rocks from 

 below. 



And it is an essential part of this theory that the materials 

 which fill the veins were forcibly injected upwards in a state of 

 complete fusion by heat. 



The third theory is that denying any subsequent processes 

 which might either cause rents and fissures, or might fill them 

 with matter which differs from the rocks which inclose them : 

 the whole formation was contemporaneous with the rocks them- 

 selves, the mineral substances which we find in veins having 

 separated and arranged themselves into the forms in which we 

 now see them to exist. 



The advocates of these theories have each zealously asserted 

 the truth of his own system, and refused to admit of causes or 

 explanations which appeared to militate against it ; and thus a 

 boundary has been set, as it appears to me, to that freedom of 

 inquiry which is so desirable in such cases, and a limit drawn 

 round the reasoning faculties of man upon evidence which may 

 come before him. 



It will appear, from what has already been said, that veins 

 have very different characters and appearances ; and this might 

 be made more clear, if it were here the proper place to enlarge 

 upon the subject and point out the distinctions. For our pur- 

 pose, however, it may be sufficient to remark upon two or three 

 principal varieties. First, then, are those which have beyond 

 all comparison been most explored and examined, on account 

 of the stores which they contain, — the metalliferous veins. As 

 these have been penetrated in all directions to the greatest ex- 

 tent that human power and ingenuity have been able to effect, 

 so their structure is better known and more accurately ob- 

 sei'ved. 



Similar to these, and occurring with them, and therefore well 

 known, are others, which, though baiTen of metals, are yet 

 often called true veins ; and these, as well as the first, come 

 pretty fully under the view of the miner. 



Next there are veins, regular in their structure to a great 

 extent, filled with matter which has the character of being de- 

 rived from igneous origin, such as are usually called dykes of 

 trap, whinstone, &c., &c. ; to which would be added by most 



