439 
Geology, 
in South America. Humboldt founds mass of platina, 
the size of a pigeon’s egg, in the alluvial soil of the 
valley of Choco in South America, along with rolled 
pieces of porphyry-slate.* 
The preceding details teach us, 
1st, That metals differ very much as to the period of 
their formation. 
. 2d, That the variety and quantity 7 of metalliferous sub- 
stances decrease in general from the primitive to the allu- 
vial period of the earth’s formation. 
3d, That molybdena, menachine, tin, scheele, cerium, 
tantalum, m an, chrome, and bismuth, are metals of the 
oldest primitive formation, and that only feeble traces of 
them are to be observed in newer periods* 
4th, That although arsenic, cobalt, nickel, silver, and 
copper, occur in old primitive mountains, they also ex- 
tend to newer mountains. 
5th, That gold, sylvan, antimony, and manganese, are 
metals of the middle age, occurring in the newer primi- 
tive, tne transition, and the oldest fleets -rocks. 
6th, That lead, zinc, and mercury, are of a very late 
date, when compared with those metals we have already 
mentioned, because they occur in greatest quantity in the 
newer or floetz formations. 
7th, That iron is found in every rock, from the oldest 
granite to the newest alluvial deposit ; hence is universal- 
ly distributed, and is therefore a production of every pe- 
riod. 
8th, That the more crystalline ores abound in the pri- 
mitive mountains, but continue decreasing in quantity 
*Vauquehn has lately discovered it in the silver-ores of 
Gaudalcanal in Spain. It is said also to have been found at 
Niznei Novogorod, six hundred German miles N. W. of Pe-' 
tersburgh. The truth ®f this report has been lately called in o.uesi 
tion. 
