Fossil Vegetation of America. 873 
very great importance to the study of fossil vegetation, let us 
remark how it agrees with other phenomena observed. 
The copper ore recently brought from New Jersey, consists 
of the blue and green carbonates and the sulphuret. This 
latter forms a kind of nucleus imbedded in the carbonates. 
From every appearance, the whole was originally sulphuret, 
the exterior of which, to a considerable depth, has been de- 
composed, and converted into these carbonates. The most 
probable cause of this conversion is the contact of the sulphuret, 
after its ejection from below, with carbonic acid dissolved in 
liquid : precisely such a liquid as might be expected to be 
formed from a surface of water with a superincumbent atmos- 
phere of carbonic acid. According to all appearance, this 
decomposition, and conversion of sulphuret into carbonates, is 
not now proceeding ; the action was probably arrested when 
the nature of the atmosphere was changed. It is not uncom- 
Mon to find sulphuret of lead converted into carbonate, but I 
have never seen any instance so clear and striking as that of 
copper ore from New Jersey. 
Crystals of carbonate of lime are often found in a state of 
mposition, and-I have several specimens on which fresh 
crystals are deposited on the half-decomposed crystal. Chem- 
ists are well aware that, although carbonate of lime is in- 
soluble in water, it is soluble in water charged with carbonic 
acid; on the supposition of an atmosphere of carbonic acid 
. Sas with which the immense extent of surface water would be 
Inpreenated, these phenomena are easily explicable. 
Nor should it be forgotten that, the density of carbonic acid 
Sas being 1524, the present atmosphere 1000, the increased 
Pressure of the column would countervail a high temperature, 
and permit the water to retain a.considerable quantity of the 
gas in solution. bonsoir 
, ,, From these considerations arise others of much importance. 
Plants growing under conditions of heat, humidity and atmos- 
Phete specially appointed for them, without reference to any 
9ther elass of animate beings, although of an organization re- 
