Reviews — J. Johfs Age of the Earth. 129 



Professor Joly read her riddle aright? The suggestion of some 

 criticisms may be excused. 



In the first place, it does not appear safe to take the intensities of 

 actions now going on as a measure of those in past ages, because tho 

 earth has been losing energy ; and, as Professor Darwin has pointed 

 out in his book on " The Tides," meteorological agencies must have 

 formerly been more powerful than they are now. In the writer's 

 opinion, in dealing with events of long past ages the interaction of 

 the moon upon the earth ought not to be lost sight of. This is 

 inversely proportional to the cube of her distance, which distance 

 was once much less than it is now, if, indeed, the moon was not 

 once a portion of the earth suddenly detached. If such was the case, 

 the prima3val condition of the earth's surface may have been pro- 

 foundly modified by the stupendous event. 



The assumption made that the primitive ocean did not contain 

 alkalies appears to require that the alumina in the original magma 

 was exactly proportioned to the alkalies, so that when the felspathic 

 minerals were formed there was neither alumina left nor alkalies, as 

 there certainly was silica in abundance, still uncombined. If this 

 proportion did not hold, there would have been either alumina 

 uncombined in the crystalline rocks, or alkalies over to combine 

 with the acids in the ocean — presumably the latter, seeing that 

 alkaline salts abound in it at present. That this due proportion 

 should have existed does not seem probable. If there was soda in 

 the priniEBval ocean, that would shorten Professor Joly's estimate of 

 the earth's age. 



The various sodium salts in the rivers are in the proportion of 

 sulphate 32, nitrate 27, chloride 17, nearly. The decomposition of 

 iron sulphide would supply the sulphuric acid. Bacteria in the 

 soils would supply the nitric. But whence came the chlorine? 

 The amount of 0-01 per cent, stated to occur in crystalline rocks 

 seems insufficient. Sodium occurs as carbonate rather abundantly 

 in some rivers and artesian wells, which, Sterry Hunt remarks, "has 

 its source in the decomposition of felspathic minerals." ^ This shows 

 that the direct product of these rocks is the carbonate rather than 

 the chloride. Is it not probable that the chlorides of sodium, and to 

 a small extent of lithium, are derived from sedimentary rather than 

 from crystalline rocks ; not from the decomposition of these rocks, 

 but from what Sterry Hunt calls the "fossil sea water still to be 

 found imprisoned in the pores of the older stratified rocks," ■ and 

 presumably in the younger as well ? 



This idea had occurred to the writer before referring to Sterry 

 Hunt's book, and he had already begun to examine a specimen of 

 the Silurian rock (Wenlock shale) obtained from the depth of 

 880 feet in the New River Company's borehole at Ware ; for it 

 seemed probable that this rock has never yet been exposed to 

 atmospheric influences, so that it would contain all the salts which 

 were present in the mud of the very early ocean from which it was 



^ " Chemical and Geological Essays," p. So. 

 2 Ibid., p. 41. 



DECADE IV. — TOL. V:r, — XO. III. 9 



