46 STUDIES, SCIENTIFIC AND SOCIAL 



hundred miles thick. It is only reasonable to suppose 

 that depression thus caused must be accompanied by a 

 corresponding elevation of some other area, and as there 

 must always be an adjacent area from which an equivalent 

 weight of rock has been removed by denudation, we should 

 expect the elevation to occur there ; and many geologists 

 believe that there is direct evidence of elevation wherever 

 areas are being rapidly denuded. 



In a very interesting letter to Natnre (Dec. 5th, 1889) 

 Mr. J. Starkie Gardner states that he has actually observed 

 the results of denudation to be of this character. He 

 says : — - 



' ' The immediate effect of cutting down cHffs, say of 100 feet in 

 height, and removing them by wave-action, is to relieve the pressure 

 at their base ; and I claim that, wherever I have excavated for the 

 purpose of collecting, under such conditions, I have found a decided 

 slope inwards away from the sea, if the strata were at all horizontal, 

 no matter what direction their general slope might be at a 

 distance from the sea margin. But on the beach, a little way 

 from the base of the cliffs, the slope is, on the contrary, towards 

 the sea. . . . This appears to me to be simply because the relief 

 from pressure has made the beach-line the crown of a slight arch, 

 and an arch that continues to grow and travel." 



Hence he concludes that — 



' ' Whether we look at the past or the present, we seem to see 

 evidence of a crust resting in equilibrium on a liquid layer, and 

 sensitive to even apparently insignificant readjustments of its 

 weight." 



The physical and geological phenomena of which an out- 

 line sketch has now been given, all point unmistakably to 

 a thin crust of various rocks resting on a molten sub- 

 stratum ; but there are certain difHculties and objections 

 which require a fuller discussion. In order to remove 

 these difficulties and answer these objections, we must, 

 with the aid of Mr. Fisher's work, go more deeply into the 

 question, and we shall then find that, by means of some of 

 the most refined inquiries of modern physicists, we are able 

 to obtain so much additional information as to the pecu- 

 liarities of the crust and of the substratum, that most, if 

 not all, of the alleged difficulties will be found to disappear. 



