THE POSITION or THE EARTH's AXIS. 115 



globe. For, as the earth is constantly going slower in 

 consequence of tidal retardation^ it would* looo million 

 years ago have rotated one seventh faster ; so that the 

 equatorial bulge would have been proportionately greater, 

 if it then existed. But the conclusion drawn has been based 

 upon a preternaturul rigidity of the earth, which is not 

 now maintained by all physicists. 



Most stress has been laid on the possibility of a change 

 by continental or local upheavals altering the centre of 

 gravity and thus changing the position of the axis ; but 

 beside this there are two which can effect a change — the 

 unequal removal of water by elevation of land displacing 

 the ocean, and, second, the removal of matter in solution ; 

 and these two I will consider, commencing with the last, 

 which works so invisibly. 



Taking, according to Mr. Mellard Reade t, about loo tons 

 of solid matter removed in solution by the drainage from 



* ' Geol. Djiiamics,' by Sir W. Thomson. 



t " On Geological Time," Pres. Address to the Livei-pool Geol. Soc, 1876- 

 77, by T. Mellard Eeade, C.E., F.G.S. These figures fell into my hands 

 after I had commenced to prepare this paper, and have been most useful ; 

 and I gladly acknowledge the great assistance they have been to me. The 

 calculations are based upon analyses given in the Sixth Eeport of the Rivers- 

 Pollution Commission for England, and such data as can be obtained from 

 other rivers which have been examined ; and this serves as a basis for calcu- 

 lation of other areas where the amount brought down has not been so care- 

 fully examined. 



Mr. Reade's paper is written to show that the rate of denudation indicates 

 that the time the sedimentary rocks have been forming is much greater than 

 is allowed by the physicists ; and according to his calculation i o miles of 

 sedimentary strata, if formed at the present rate of denudation, would require 

 526 million years ; and he also points out how long it would require to derive 

 the salts in solution in the ocean at the present rate, and says that it would 

 require 200 million years to renew the chlorides. This is a most useful paper, 

 as showing how great a length of time is required, and certainly does carry 

 the organic life on the globe very far back; but I think bis figures will require 

 modification by such considerations as the amount dissolved by the ocean from 

 the detritus and erosion of the coast and subaqueous eruptions, the former 

 greater rainfall, higher tides, and the warmer water holding more salts in 

 solution. 



I 2 



