820 



SCIENCE. 



[Vol. II., No. 47. 



the briglitest part of lliis band, as sho^ni iu the accom- 

 panying figure. 



"In tbis diagram {ot a normal spectrum), curve a 

 [w'hicb Mr. Capron calls the phosphorescence curve] 

 is deduced from the spectrum of phosphoretted hydro- 

 gen, curve b from Professor Angstrom's spectrum of 

 the violet pole of air-vacuum tubes; a tt is the princi- 

 pal auroral line." This figure is apparently intended 



to represent the facts under ordinary laboratory con- 

 ditions; but Mr. Capron states, that according to Le- 

 coq de Boisbaudran, when the flame of phosphoretted 

 hydrogen is artificially cooled, the bands of the spec- 

 trum become intensified, and in such a way that the 

 brightest portion of each hand is shifted toward the 

 red end of the spectrum. Mr. Capron appears to 

 think, tliat, under the intense cold of the auroral re- 

 gions, one of these bands might become the line a u. 

 E. H. Hall. 



LETTERS TO THE EDITOR. 

 Secular increase of the earth's mass. 



The thoughtful and suggestive researches of Ebel- 

 men and T. Sterry Huntrou the chemical and geo- 

 logical relations of the earth's atmosphere, ' have led 

 me to some further deductions, which seem to in- 

 crease the interest in. this field of inquiry. The gen- 

 eral tendency of these studies is to show that the 

 chemical transformations in progress upon the earth 

 involve the fixation of a larger volume of atmos- 

 pheric constituents than could probably have ever 

 existed in the atmosphere at one time, and that they 

 must consequently have arrived from interplanetary 

 space. ' 



1. The carbonates. —It is generally agreed, as first 

 shown by Hunt, that the carbonates of lime and 

 magnesia have arisen chiefly through the interactions 

 between carbon dioxide of the atmosphere, the decora- 

 posing silicates of the earllrs crust, and the chloride 

 of caJcium of the ocean. The carbon dioxide has 

 therefore been contrilnited by the atmosphere. To 

 what does this contribution amount? We may as- 

 sume, without material error, that the carbonates here 

 in question are all calcium carbonate, with a specific 

 gravity of 2. 72. Then, the mean pressure of the at- 

 mosphere beino: about 14.7 pounds avoirdupois on a 

 square inch, a little calculation shows that an amount 

 of carbon dioxide iu the atmosphere suflicient to 

 double its pressure would yield only 8.627 metres of 

 limestone. An amount suflicient to cause a pressure 

 of 80 atmospheres would suffice for the formation of 

 limestones equal to only a fortieth (.022(15) of the 

 hundred thousand feet which, for this jiurpose, may 

 be assumed as the thickness of the stratified rocks. 

 But a pressure of 80 atmospheres at a temperature 



I See a memoir by T. Sterry Hunt in Amer.jonm. sc, May, 

 1880, where references are given to numerous other publications. 



of ;W° C. produces liquefaction of carbon dioxide. 

 The actual proportion of limestones and dolomites in 

 the earth's crust is about one-eightli, as I have shown 

 by recent studies. This amount would yield, by the 

 liberation of all its carbon dioxide, a pressure of 441.0 

 atmospheres. If we consider the limestones and dol- 

 omites formed since the period of the coal-measures, 

 the proportion required to yield, on the liberation of 

 its carbon dioxide, a pressure of 80 atmospheres, 

 would be only a twenty - second 

 (.04469) of all the post-carboniferous 

 strata. The actual proportion is 

 about one-eighth, as for the whole 

 stratified crust; and this would yield 

 sufficient carbon dioxide to cause a 

 pressure of 223.8 atmospheres. 



It is not credible that such amounts 

 of carbon dioxide have ever existed 

 in the atmosphere at one time. Dur- 

 ing the larger part of the aeons of car- 

 bonate formation, animal life has existed in great 

 abundance upon the earth ; and this would have been 

 impossible with 200 to 400 atmospheres of carbon di- 

 oxide present. As the proportion of this gas in thr 

 existing atmosphere is only 4-} parts in 10,000 b> 

 weight, 200 atmospheres of the gas would be 444,000 

 times the present proportion. It is scarcely more 

 credible that the pressure of 200 to 400 atmospheres 

 would have been compatible with either vegetable or 

 animal organization, so similar as it was fundamen- 

 tally to modern organization. As this large amount 

 of carbon dioxide cannot be supposed derived from 

 the earth's crust, it must have been derived from in- 

 terplanetary space. This would imply an addition to 

 the earth's mass of .0003806, which is about -j-^;')-!; part 

 of the present mass. 



2. The kaoUnization of felspars. — Hunt has show u 

 that the kaolinization of a layer of 51.66 metres of 

 orthoclase, or its equivalent of quartzo-felspalhic 

 rocks, would result in 23.7 metres of kaoline, and 

 would use up 10,333 kilograms of carbon dioxide per 

 square metre of surface. This is the weight of the 

 atmosphere. Now, the whole amount of felsjiathic 

 decomposition during the sedimentary ages must 

 much exceed 500 metres in vertical thickness of kao- 

 linic deposits. But 500 metres of kaoline represent 

 21.1 atmospheres of carbon dioxide; and, assuming 

 the mass of the atmosphere atTr.inTrmi in relation to 

 the earth, the carbon dioxide fixed in the processes of 

 kaolinization would be .0000175826 of the total mass 

 of the earth. 



3. Decay of hornblende, pyroxene, and olwine. — Ac- 

 cording to Hunt, the decay of lOj metres of such 

 minerals, or their equivalents in hornblendic and py- 

 roxenic rocks, would yield carbon dioxide equal to 1 

 atmosphere: hence, if the earth's crystalline rocks 

 have afforded 500 metres of hornblende and pyroxene, 

 they must have fixed 48.387 atmospheres oJE carbon 

 dioxide. This, in relation to the earth's mass, is 

 .0000403209. 



4. Conversion of ferrous inio ferric oxide. As Ebel- 

 men states, the conversion of 21, HS" kilograms of fer- 

 rous oxide into 23,750 kilograms of ferric oxide would 

 consume the whole of the 2,376 kilograms of oxygen 

 in the atmosphere (more exactly, 1.007 atmospheres) 

 covering a squai'e metre. If, then, we suppose tlie 

 existence over the earth of 1,000 metres of sediments 

 derived from the decay of crystalline rocks contain- 

 ing only one per cent of ferrous oxide, weighing, 

 according to Hunt, 25,000 kilograms, this is 1.052 

 times the amount requisite to fix the oxygen in 

 1.007 atmospheres; that is, 10 metres of ferric 

 oxide represent the fixation of 1.059 atmospheres of 



