740 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



series of rocks, but that it shares its formation with the meta- 

 phoric, such as the talcose and argillaceous, giaywacke, green- 

 stone, mica and gneiss schists, which can be proved by specimens 

 he brought from California. Hitchcock states that gold and plat- 

 inum always occur in metallic states, and thej usually have been 

 explored in drift. They are often associated with other rocks, 

 and in this country especially, a gold deposit has been traced from 

 Canada to the southern part of Georgia, and the metal is embraced 

 in the talcose slate formation, in veins usually of quartz. The 

 same is in California, although eruptive rocks are there more com- 

 mon. Dana saj's that nine-tenths of all the rocks of the globe 

 have been formed at the close of the Palasozic period (silurian, 

 devonian and carl)oniferous,) and before the Mesozoic, or Reptiles. 

 During the I'evolution that followed, these beds, besides undercfoins 

 in many regions an extensive crystallization, were also supplied 

 with mineral wealth. Much of the gold of the world comes orig- 

 inal ly from rocks which were metamorphosed and filled with veins 

 at this time. None pf the precious metals are known to occur in 

 the crystalline azoic. The veins of gold quartz which contain the 

 gold were brought forward through fissures of the slate, but were 

 not filled up from below by injection, an idea offered to account 

 for the formation of metalliferous veins, but b}'' long continued 

 heat, accompanied by uplifting and disturbance of the beds. 



The geysers and other great volcanic eruptions have probably 

 produced the immense metamorphizatiou of such minerals as are 

 associated with the gold-bearing quartz veins, such as iron pyrites. 

 The continued heat beneath the, ocean, must have produced a 

 decomposition of the sulphur and iron from the pyrites, and dis- 

 solved either the silica or produced fissures, in which the native 

 gold found a place. When young. Dr. Feuchtwanger supposed 

 that as gold is six times specifically heavier than any crystalline or 

 other metamorphic minerals, and it being only found in its native 

 state with platinum, (which is twenty-one, gold being nineteen, and 

 all other rocks, crystalline and metamorphic, 2-5 specific gravity,) 

 both metals must naturally have been thrown out by central fire 

 from the spheroidal crust along with the igneous rocks in their 

 original fluidity, but which settled down first on account of their 

 great specific gravity. It is generally supposed that the volcanic 

 eruptions have produced metamorphose or transformation, and 

 Leibnitz's theory, promulgated in 1680, that our whole planet was 



