Vol. 59.] THE FIGI7KE OP THE EA.ETH. 187 



moon exerted a pressure on the earth's surface of 5000 lbs. to 

 the square inch. A permanent cyclonic system would exist over 

 that region of the earth which immediately faced the moon, and 

 this may have had much to do in determining the general distri- 

 bution of atmospheric pressure over the earth's surface. This 

 again may have assisted in determining the distribution of those 

 depressions of the general level which we imagine to have initiated 

 the ocean-basins. The oceans themselves weighting those portions 

 of the crust over which they accumulated may have helped to 

 preserve something of its original form ; but this has undergone 

 very considerable modifications, chiefly through the breaking-down 

 of the greater protuberances. The position and extent of the 

 subsiding areas would depend upon the strength of the crust and 

 the slope of its inequalities. That the fractures by which at some 

 stages re-adjustment has taken place have frequently been circular 

 arcs is shown by observation, and there is much evidence to suggest 

 that such fractures have frequently preceded as well as followed 

 the folding-up of a mountain-chain. 



This study, although it has long occupied my attention, is far 

 from being as complete as it might easily be made ; but I am led to 

 submit it to the Society at the present stage by finding that similar 

 but in some respects much more exactly-expressed ideas have lately 

 been brought forward by Mr. J. H. Jeans in a memoir read before 

 the Eoyal Society on December 4th, 1902, the preliminary abstract of 

 which appears in the Proceedings of that Society, vol. lxxi, p. 136. 

 Mr. Jeans has treated the subject mathematically, and concludes 

 that the ' pear-like shape,' as he happily expresses it, might very 

 possibly have been possessed by the earth at the time of its 

 consolidation ; he suggests that Australia may represent the 

 ' stalked end ' of the ' pear,' the depths of the surrounding ocean 

 its w waist,' and the land-hemisphere its ' broad end.' The mor- 

 phological axis would have one pole near the British Isles and the 

 other between New Zealand and the Antarctic Ocean. This 

 correlation is less symmetrical than that which has been imagined 

 in the present contribution, and in one respect reverses it, for we 

 have supposed the Pacific to cover the broad end of the pear, the 

 continental belt to correspond with its sides, the Indian, Atlantic, 

 and Mediterranean Oceans with its waist, and Africa with the 

 stalked end. This reversal, however, is of less importance than 

 the recognition of a uniaxial symmetry. 1 On this point we seem 

 to be in complete agreement, and it is not a little singular that two 

 persons approaching the subject from such extremely different 

 points of view should have reached essentially similar conclusions. 



1 [Since this paper was read Mr. Jeans and I have corresponded by letter on 

 this point. His view with regard to the broad end is evidently the right one, 

 it must be represented by the land-hemisphere. The small end will therefore 

 correspond to the oceanic floor from which the islands of the Central Pacific 

 rise, ' the mightiest of all the submarine buckles of the earth-crust,' Lapwortli, 

 Presid. Address to Sect. 0, Eep. Brit. Assoc. 1892 (Edinburgh) p. 705 — 

 W. J. S., March 16th, 1903.] 



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