274 SEE— FURTHER RESEARCHES ON [April 24, 



neath the crust, chiefly when it is expelled from under the sea, which 

 shakes down cities and devastates whole countries. 



39. This expulsion of lava under the land can mean nothing else 

 than the secular leakage of the oceans, because the mountains along 

 the coast which are rent by the shaking of the earth till they break 

 into volcanoes, emit chiefly vapor of steam. Moreover the unsym- 

 metrical shape of the mountain folds, showing the gentler slope 

 towards the shore, indicates that the folds of the crust were pushed 

 from the direction of the sea. This was produced by the expulsion 

 of lava under the crust arising from the secular leakage of the 

 ocean bottom. 



40. By the study of seismic and other phenomena now observed 

 in the great laboratory of nature we may penetrate the deepest 

 secrets hidden beneath the earth's crust, to which no mortal eye can 

 ever bear direct witness. And these researches may greatly increase 

 the safety of whole communities, and especially of cities and of 

 commerce, throughout the world, by enabling us to guard against 

 the dangers of earthquakes and seismic sea waves. This appro- 

 priate use of the laboratory of Nature is one of the ultimate objects 

 of natural philosophy. 



Blue Ridge on Loutre, 



Montgomery City, Missouri, 

 February 19, 1908. 



POSTSCRIPT. 



In a paper read before the Royal Society in 1902, Professor 



J. H. Jeans, formerly of Cambridge, now of Princeton University, 



has the following theory of earthquakes : 



" It seems to be ahnost certain that the present elastic constants of the 

 earth are such that a state of symmetrical symmetry would be one of stable 

 equilibrium. On the oilier hand, if we look backward through the history 

 of our planet, we probably come to a time when the rigidity was so much 

 that the stable configuration of equilibriums would be unsymmetrical. At 

 this time the earth would be pear-shaped and the transition to the present 

 approximately spherical form would take place through a series of ruptures. 

 It is suggested that the earth, in spite of this series of ruptures, still retains 

 traces of a pear-shaped configuration. Such a configuration should possess 

 a single axis of symmetry, and this, it is suggested, is an axis which meets 

 the earth's surface somewhere in tlie neighbourhood of England (or pos- 

 sibly some hundreds of miles to the southwest of England). Starting from 



