GEOLOGY. 275 



was being separated along the shores of the great palaeozoic ocean, 

 the shales and limestones of the Quebec group were accumulating in 

 deeper waters. Mr. Hunt further considers the well-known Ver- 

 mont marbles of Dorset and Rutland as identified with the limestone 

 of the Quebec group, and as beds of chemically precipitated carbon- 

 ate of lime, or travertine, and not limestone of organic origin. 



The Quebec group is of considerable economic interest, inasmuch 

 as it is the great metalliferous formation of North America. To it 

 belongs the gold which is found along the Appalachian chain from 

 Canada to Georgia, together with lead, copper, zinc, silver, cobalt, 

 nickel-chrome and titanium. 



The immense deposits of copper ores in eastern Tennessee, and 

 the similar ones in Lower Canada, both of which are for the most 

 part in beds subordinate to the stratification, belong to this group. 

 The lead, copper, zinc, cobalt, and nickel of Missouri, and the copper 

 of Lake Superior, also occur in rocks of the same age, which appears 

 to have been preeminently the metalliferous period. 



The metals of the Quebec group seem to have been originally 

 brought to the surface in watery solution, from which we conceive 

 them to have been separated by the reducing agency of organic mat- 

 ter in the form of sulphurets, or in the native state, and mingled with 

 the contemporaneous sediments, where they occur in beds, in dissem- 

 inated grains forming fahlbands, or are the cementing material of 

 conglomerates. During the subsequent rnetamorphism of the strata 

 these metallic matters, being taken into solution by alkaline carbon- 

 ates or sulphurets, have been redeposited in fissures in the metal- 

 liferous strata, forming veins, or, ascending to higher beds, have given 

 rise to metalliferous veins in strata not themselves metalliferous. 

 Such we conceive to be, in a few words, the theory of metallic depos- 

 its ; they belong to a period when the primal sediments were yet im- 

 pregnated with metallic compounds which were soluble in the perme- 

 ating waters. The metals of the sedimentary rocks are now however 

 for the greater part in the form of insoluble sulphurets, so that we 

 have only traces of them in a few mineral springs, which serve to 

 show the agencies once at work in the sediments and waters of the 

 earth's crust. 



The intervention of intense heat, sublimation and similar hypothe- 

 ses to explain the origin of metallic ores, we conceive to be uncalled 

 for. The solvent powers of solutions of alkaline carbonates, chlo- 

 rides, and sulphurets, at elevated temperatures, taken in connection 

 with the notions above enunciated, and with De Senarmont's and 

 Daubree's beautiful experiments on the crystallization of certain min- 

 eral species in the moist way, will suffice to form the basis of a satis- 

 factory theory of metallic deposits. 



In Eastern Canada, Messrs. Logan and Hunt recognize a group of 

 strata which they designate as the " Quebec group," which have for 

 their base a series of black and blue shales, and are succeeded by 

 gray sandstones, great beds of conglomerate, with magnesian and 

 pure limestones. These are associated with beds of fossilliferous lime- 

 stones, and with slates containing graptolites, and are followed by a 

 great thickness of red and green shales, often niagnesiau, and over- 

 laid by two thousand feet of green and red sandstone, known as the 



