18 SMITHSONIAN MISCKLLANEOUS COLLECTIONS VOL. 56 



llian tlie actual ■luicoi'taintios of the computation. If, for tlie sake of 

 nnifoi-mity, we take as the crude a<>'c of the ocean the quotient (Irst ob- 

 1 11 i lied, 80,726,000 years, the chemical precipitates are represented by the 

 follov\'iii<;- anmial (|iiantilies : 



SO, 288,017,000 metric tons 



Ca 550,822,000 



Mg 71,945,000 



K 34,971,400 



RsOa 75,213,000 



Si02 319,170,000 



Combined, the radicles thns ])r('(i|)itnti'd in the ocean, yield the follow- 

 im^- substances: 



Gyi)sum, CaSO, . 2mO 516,020,000 metric tons 



Calcium carbonate, CaCO:.. . 1,077,030,000 

 Maynesiura carbonate, MgCOj 249,587,000 

 Limonite,^ 2 FeA ■ 3HoO . . 87,505,000 

 Silica, SiOa 319,170,000 



The ])otassiuin remains unaccounted for. Part of it is taken up by the 

 clay-like substances in the oceanic silts, and part goes to form glauconite; 

 but it is not wortli while to speculate ujion the relative pi'oportions of 

 potassium Avithdrawn by these two processes from solution. 



The figures given above for the quantities of the five chemical precipi- 

 tates annually deposited in the ocean can, of course, make no pretense to 

 accuracy. They are merely rougli aj^proximations to the truth, but they 

 tell something of the relative magnitudes. Even if we knew precisely the 

 age of the ocean, it would not be practicable to reckon backward and so 

 to determine the total mass of deposits formed during geological time. 

 The figures tell us what is happening to-day, but are inapplicable to the 

 past. The reason for this statement is, that apparently the ditferent 

 deposits have formed at different rates. In the beginning of chemical 

 ei'osion fresh rocks were attacked, and relatively more silica and less lime 

 passed into solution. At present, limestones, laid (lown in previous 

 geologic ages, are being dissolved, and calcium is added to the ocean more 

 rapitlly than in pre-Cambrian times. This is not mere speculation. A 

 study of river waters with reference to their origin, whether from crystal- 

 line or sedimentary rocks, fully justifies my assertions. 



The vexed question as to the source of oceanic chlorine, I have so far 

 left out of consideration. Dr. Becker has shown that volcanic agencies 

 are adequate to account for it. Some, however, may have come from 

 ferrous chloride, lawrencite, a comi^ound which is common in meteoric 

 irons. If our planet is analogous to a great meteorite, lawrencite must 



* Assuiningr R0O3 to be nil FeoOa. It is certainly, in part, .\l2O3. 



