REVIEWS, 



455 



In the consideration of tlie mechanical or transporting action of water, we have, 

 besides the operations effected by its upward flow, to consider those effected by its 

 percolation downwards, 



V/hcn the waters sink into the ground they carry downwards such soluble salts 

 as they meet with on the surface or beneath the soil, and deposit them either in 

 this course or on meeting with other water holding different salt in solution. 



"And here the question may be asked, What becomes of all the metals that are 

 raised by man to the surface of the earth ? England alone produces nearly three 

 millions of tons of iron annually ; while the aggregate of all the metals produced 

 throughout the world would startle the mind, and task the eye by its long array 

 of figures. Year after year this active production has been in operation, from the 

 days of Tubal Cain to the present time ; greatly increased, it is true, in the past 

 few centuries ; and if but a tithe of the whole amount ever produced was now in 

 existence, the whole surface of the globe would, or could, be encased with a dense 

 covering of solid metal. In the beautiful economy of nature nothing is lost, 

 nothing annihilated ; and in the comminution by actual use, for every contact 

 with a metal causes a wear upon its surface, — in the chemical action of the 

 atmosphere, with its mechanical alternating effect by changes of temperature, — 

 and in the solvent and mechanical properties of the Avater, re-conveying the 

 metallic particles and salts to the interior of the earth, may, perhaps, be found the 

 only satisfactory solution of the inquiry." 



The third division of the inquiry is in its electro-magnetic bearing, and opens a 

 wide and little-explored field of inquiry, but which promises to "throw open to the 

 researches of the student truths of the highest and most fascinating character," 

 and presenting " scope for the boldest strides of genius." 



" Why is it, that during its position in the vein, and attached to or forming a 

 portion of the vein-rock, that fragment, which when broken off, so speedily under- 

 goes a change in its chemical, and consequently in its physical construction, 

 should remain unaltered? If any change could be perceptible in it, while in its 

 original position, it would be that of an increased metallic value. There would, 

 if it were examined in a vital portion of the vein, be found a gradual accumula- 

 tion of metallic particles. Let us take a fragment of pyritous ore— auriferous 

 pyrites, and, before being abraded from the vein-rock, the pyrites is of a bright 

 glistening surface, hard, firm, and glass-like in its brittleness, vfitli no visible 

 appearance of the gold, and to the inexperienced eye it would present no feature 

 of intrinsic worth. It is broken from the vein-rock, and without being removed 

 from the adit-level in which it was obtained, it is allowed to remain under the 

 surface of the flow of Avaste vein-water which passes along the ' floor ' of the level. 

 But a few days shall have elapsed since its separation from the rock, and yet an 

 oxidation of the iron of the sulphuret will be found to have commenced. The 

 bright surface of the pyrites appears covered with a ferruginous rust, but still no 

 gold is visible. The oxidation, as time passes, will be found to increase, and the 

 brightened colour of the specimen will show that its iron has passed from the 

 condition of a sulphuret to that of a peroxide. In its physical character it will 

 be found to have passed through a wide mutation. It is no longer compact and 

 indurated, but is a slightly cohesive mass, which, under the lightest friction, falls 

 into a soft, partially-gritty powder, intermixed with which are plainly discernible 

 the glistening particles of the yellow gold. This is not a surmised case ; it is a 

 true picture of a phenomenon that is continually witnessed by the workers in gold- 

 veins. Why, I repeat, is the pyrites kept from decomposition, while forming a 



