JJO THIRD REPORT — 1833. 



in Mexico and Peru are said to be less rich as they descend 

 further, those of Derbyshire and Cornwall exhibit the very 

 contrary. 



He is unfortunate in this allegation, and the facts will not 

 bear him out, as every one of common experience must know ; 

 and thus, as I have before observed, we have hypotheses sup- 

 ported by a limited knowledge of the facts. 



The theory of the filling up of veins by precipitation from 

 aqueous solutions, is defective in not being able to show what 

 menstruum could render such substances soluble in water ; 

 and this difficulty must remain an important one, unless en- 

 larged knowledge should hereafter afford the means of ex- 

 plaining it. 



But when we are told that the supposition is absurd, that 

 water cannot arrange its deposits in planes highly inclined, that 

 no appearance of stalactites is to be found in veins, nor can 

 we see in them any substance like those on the earth's surface, 

 which aqueous action has removed, — it must be recollected that 

 we know silex is soluble in water at high temperatures ; that 

 crystals do arrange themselves on the sides of vessels in planes 

 highly inclined; that stalactites of chalcedony, of quartz, and of 

 iron pyrites, have been found deep in the veins in Cornwall, and 

 that much of the substance of the surrounding rocks, and such 

 as we see on the surface, and adjoining and inclosing the veins 

 themselves, is found in them, occupying much of their space, 

 previously having been worn down into fragments, into loose 

 sand, and into clay or mud, the latter of which is so common 

 that, as I have before observed, it is relied on by the miner as 

 a distinguishing character of regular veins*. 



The action of water may, I think, be as fairly assvimed as 

 that of fire ; and we may consider what their joint powers might 

 be, when compelled, as it were, to act together, under circum- 

 stances that immense pressure might produce. 



But in examining the contents of veins, we are, I think, likely 

 to be struck, not only by the appearance of a complication of 

 causes, but by evidence of their succession, admitting the pro- 

 bability not only of different agents having been employed, but 

 of their having done their work separately as well as conjointly, 



• Mr. Weaver describes the contents of the great vein of Bolanos in Mexico 

 thus : " The chief mass of this vein may be said to consist of tlie detritus of the 

 adjacent rocks, more or less consolidated, and generally hard ; nay, in places, 

 it is actually composed of a conglomerate. Proper vein-stones, such as fluor 

 or calc spar, are, comparatively speaking, casualties. In this basis the finer 

 delicate silver ores and native silver are dispersed, in common with the harder 

 and coarser ores of blende, iron, and copper, besides lead ores." 



