i6
��THE SCIENTIFIC MONTHLY
��earth we must deduct all those portions of mineral deposits which as they exist to-day are mainly of organic origin, such as the organic carbonates and phosphates of lime/® the carbonaceous shales as well as the carbonaceous limestones^ the graphites derived from carbon^ the silicates derived from diatoms, the iron deposits made by bac- teria, the humus of the soil containing organic acids, the soil derived from rocks which are broken up by bacteria, and even the ooze from the ocean floor, both calcareous and siliceous, formed from the shells of f oraminifera and the skeletons of diatoms. Thus, before the appear- ance of bacteria, of algse, of foraminifera, and of the lower plants and lowly invertebrates, the surface of the earth was totally different from what it is at present; and thus the present chemical composition of ter- restrial matter, of the sea, and of the air, as indicated by Table I, is by no means the same as its primordial composition sixty million years ago.
��TABLE I
AvxBAGs Distribution of ths Elements in Eabth, Am and Water at
Present Tiicesi
��Oxygen.
��SUicon
Aluminum.
Iron ,
Calcium. . . , Maffncsium,
Sodium
Potasnum. , Hydrogen. ., Titanium . . , Carbon. . . . , Chlorine.. ..
Bromine
Phoephorue . Sulphur,, . . Barium. . . , Manganese. Strontium . . Nitrogen
��Fluorine
All other elements.
��Ltttaosifliera,
�Hydrosphflra.
�9S Per Cent.
�7 Per Cent.
�47.17
�85.79
�28.00
� �7.84
� �4.44
� �3.42
�.05
�2.27
�.14
�2.43
�1.14
�2.49
�.04
�.23
�10.67
�.44
� �.19
�.002
�.06
�2.07
�• • ■ •
�.008
�.11
� �.11
�.09
�.09
� �.08
� �.03
■ • ■ •
� �.10
� �.50
� ��Atmotpbere
��20.8 (variable to some ex- tent)
��variaUe
��variable
��78.0 (variable to some ex- tent)
��AverMPe*
Inelttdlng
Atmcwphflra
��49.85
��26.03
7.28
4.12
3.18
2.11
2.33
2.33
.97
.41
.19
.40
.10 .10 .09 .08 .03 .03
��.10 .47
��80 It seems improbable that organisms originaUy began to use carbon or phosphorus in elementary form: carbonates and phosphates were probably avail- able at the very beginning and resulted from oxidations of decompositions. — ^W. J. Gies.
Phosphate of lime, apatite, is an almost ubiquitous component of igneous rocks, but in very small amount. In more than a thousand analyses of such rocks, the average percentage of PsOs is 0.25 per cent. — ^F. W. Clarke.
•1 Clarke, F. W., 1916, p. 34.
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