806 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



deeply buried beneath its own ruins ; and it can be demonstrated 

 that this crust must have been totally unlike granite, which in all 

 cases had a sedimentary and aqueous origin, although, like other 

 softened rocks, it often assumes an eruptive or scotic form. It can 

 be proved that the crystalline rocks of New England were at one 

 time buried beneath sedimentary strata at least two or three miles 

 in thickness, which were, long ages ago, removed by denudatioy 

 to build up rock formations in other regions. 



Geology of the Metals. 

 The metals were doubtless dissolved in the waters of the primeval 

 sea at its formation, and in great part precipitated in its early 

 sediments to be again dissolved by infiltrating waters and brought 

 to the earth's surface. From their soluble oxydized condition 

 they have been reduced by organic matters, sometimes to the 

 metallic state, as in the case of the copper of Lake Superior, but 

 more generally to the condition of sulphurets. Whenever decay- 

 ing organic matters encounter sulphates which abound in sea water, 

 they give rise to sulphides or sulphureted hydrogen, which is 

 nature's great agent for preci^Ditating metals and removing them 

 from the terrestrial circuLation. Hence we find, in various rocks, 

 sulphurets of iron, copper, zinc and other metals, sometimes in 

 considerable proportion, forming workable beds of ores, but more 

 generally sparingly disseminated. Nature's way of concentrating 

 these sparsely scattered metallic matters is to dissolve them out 

 by certain mineral wafers, generally when the waters are deeply 

 buried ; these waters ascending through joints or fissures in the 

 rocks, and gradually becoming cooled or changed, deposit upon 

 the walls of these then dissolved matters in the shape of ores, often 

 mixed with spars and other minerals which constitute the vein- 

 stones. Experiments shoAv that alkaline bi-carbonates and sulphids 

 which abound in the hot mineral Avaters are the proper solvents 

 for the diifused metals, and this process of concentrating the 

 metals in veins is doubtless now going on in portions of the earth's 

 crust. 



Natural "Waters. 

 Mineral waters are in part derived from decomposing rocks, but 

 in part also from the water which impregnates the buried marine 

 sediments, and is really fossil sea-water. This, more or less modi- 

 fied or diluted by admixture, forms most saline mineral waters. 

 The amount of water imprisoned in the unaltered sedimentary 



