and Production of Raised Beaches. 207 



change, however small, in order to rectify the balance. For if the 

 halance was not perfect, motion must necessarily ensue, either up or 

 down as the case might require. 



The earth is such a large solid mass that we are apt to look upon 

 it as perfectly immovable and rigid, and for all practical purposes no 

 doubt it may be so considered. But in the great operations of nature 

 with which geology has to deal such is not the case, and changes of 

 pressure so small as to produce no visible effect to ordinary observation 

 wiH, when continued for thousands of years, occasion changes that 

 are manifest to all. In the following remarks we wish to draw 

 attention to some results that have not, apparently, attracted the notice 

 they deserve. 



In a recent paper ^ I mentioned that one of the most obvious effects 

 continually in progress is the denudation of the land by rain, rivers, 

 and glaciers. These are always at work, wearing away the surface 

 and transporting material down to the sea. Here, therefore, we have 

 a process constantly going on which tends to lessen the weight of 

 the land so that it will no longer balance the upward pressure ; 

 consequently the land will be forced up, and this rise of the land will 

 help to compensate for the denudation which would otherwise in course 

 of time tend to level down the continents altogether. 



From the amount of sediment supposed to be annually carried into 

 the sea by the Mississippi, CroU calculated that on an average about 

 one foot in depth over the entire surface of a continent would be worn 

 away in the course of 6,000 years. ^ Of course, this is only a very 

 doubtful approximation, for the annual quantity of sediment carried 

 into the sea by a large river is a matter very difficult to ascertain 

 with any approach to accuracy ; but it will serve to show the direction 

 in which things are moving. The denuding action will evidently go 

 on most energetically where there is a heavy rainfall and a rapid 

 slope on the surface. The earth's action ^ may be compared to 

 that of a spring of enormous strength, on which the surface load 

 exerts a downward pressure. When we lessen the pressure on this 

 spring the result must inevitablj^ be a rise, which will show itself 

 in a change of the relative level of sea and land ; and here comes in 

 the point to which we desire to draw attention. The raised beaches 

 observed on so majiy coasts may probably find their explanation in this 

 action ; but I am not aware that such a connection has ever been 

 mooted.* Upheavals by volcanic action and obscure subterranean 

 forces have been invoked, but no relation has been drawn between 

 the existence or the varying level of these beaches and the denudation 

 of the adjoining lands, whereas an interesting connection of this nature, 

 I think, may be pointed out. 



Taking the case of Scotland, we have raised beaches all round it, 

 and I have elsewhere ^ endeavoured to show that on the east side, as 



1 Ibid., p. 486. 2 QpoL. Mag., November, 1905, p. 485. 



^ Lyell, " Student's Elements of Geology," 2nd ed., p. 91. 



* [See papers by Dr. C. Eicketts, " Subsidence Effect of Accumulation" : Geol. 

 Mag., 1872, p. 119; 1873, p. 141; 1883, p. 93; 1883, pp. 302, 348, etc. 

 J. S. Gardner, op. cit., 1881, p. 241 and Plate, p. 289.— Edit. Geol. Mag.] 



^ Journ. Geol. Soc, vol. xxi (1865), p. 190 ; Geol. Mag., January, 1906, p. 23. 



