630 GOLD OF AUSTRALIA. [Ch. XXXVIII. 



mian conglomerates which, lie at the base of the Ural Mountains, although 

 large quantities of iron and copper detritus are mixed with the pebbles of 

 those Permian strata. Hence it seems that the Uralian quartz veins, con- 

 taining gold and platinum, were not formed or certainly not exposed to 

 aqueous denudation during the Pennian era. 



In the auriferous alluvium of Russia, California, and Australia, the 

 bones of extinct land-quadrupeds, have been met with, those of the mam- 

 moth being common in the gravel at the foot of the Ural Mountains, 

 while in Australia they consist of huge marsupials, some of them of the 

 size of the rhinoceros and allied to the living wombat. They belong to 

 the genera Diprotodon and Nototherium of Professor Owen. The gold 

 of Northern Chili is associated in the mines of Los Homos with copper 

 pyrites, in veins traversing the cretaceo-oolitic formations, so called be- 

 cause its fossils have the character partly of the cretaceous and partly of 

 the oolitic fauna of Europe.* The gold found in the United States, in 

 the mountainous parts of Virginia, North and South Carolina, and Georgia, 

 occurs in metamorphic Silurian strata, as well as in auriferous gravel de- 

 rived from the same. 



Gold has now been detected in almost every kind of rock, in slate, 

 quartzite, sandstone, limestone, granite, and serpentine, both in veins and 

 in the rocks themselves at short distances from the veins. In Australia 

 it has been worked successfully not only in alluvium, but in veinstones in 

 the native rock, generally consisting of Silurian shales and slates. It has 

 been traced on that continent, over more than nine degrees of latitude 

 (between the parallels of the 30° and 39° S.), and over twelve of longi- 

 tude, and yields already an annual supply equal, if not superior, to that 

 of California ; nor is there any apparent prospect of this supply diminish- 

 ing, still less of the exhaustion of the gold fields. It seems reasonable, 

 therefore, to share the anticipations of M. Delesse that the time will come, 

 and cannot be very remote, when a marked depreciation will be experi- 

 enced in the value of this metal.f 



It has been remarked by M. de Beaumont, that lead and some other 

 metals are found in dikes of basalt and greenstone, as well as in mineral 

 veins connected with trap rocks, whereas tin is met with in granite and 

 in veins associated with the granitic series. If this rule hold true 

 generally, the geological position of tin in localities accessible to the 

 miners, will belong, for the most part, to rocks older than those bearing 

 lead. The tin veins will be of higher relative antiquity for the same 

 reason that the "underlying" igneous formations or granites which 

 are visible to man are older, on the whole, than the overlying or trap- 

 pean formations. 



.If different sets of fissures, originating simultaneously at different 

 levels in the earth's crust, and communicating, some of them, with 

 volcanic, others with heated plutonic masses, be filled with different 



* Darwin's S. America, p. 209, <fcc. 



f Annales des Mines, 1853, torn. iii. p. 185. 



