208 Dr. T. F. Jamieson — Changes of Level and Raised Beaches. 



we trace the beach northward, the elevation gradiially lessens from 

 about 30 feet along the Firth of Forth to about 17 feet at ^lontrose and 

 8 feet or so at Aberdeen ; a result which harmonizes with the smaller 

 denudation that we might expect from the lesser rainfall along the 

 valleys as we go north. In tracing the beach inland along the Forth 

 we find its elevation increasing somewhat as we go up, and here again 

 the result harmonizes with the theory. Again, on the West of 

 Scotland we have higher beaches corresponding to the heavier rain 

 along that side of the country. In the Shetland Islands, on the other 

 hand, Messrs. Peach and Home ' particularly remarked the entire 

 absence of any raised beaches. T^ow this is just the very thing we 

 should expect on the theorj- here advanced, for the deniidation 

 caused by the rainfall there must be too slight to cause any noticeable 

 rise. Islands, however, close to a mainland or continent would 

 probably move up or down with the adjoining land, for unless they 

 were some distance off they probably would not move independently. 

 But the absence of these beaches in Orkney, and more particularly in 

 Shetland, is an interesting and important fact which harmonizes so 

 well with the explanation now offered that I am inclined to think this 

 theory may prove to be the true one. Indeed, when one considers 

 the frequent occurrence of raised beaches along the coasts of the 

 world it seems difficult to account for them so well in any other way ; 

 for I fail to see how such widespread elevations of small amount could 

 be effected all along the margins of our continents by the causes 

 commonly assigned, whereas the denudation everywhere going on by 

 rain and rivers is just such a universally present action as we require. 

 Without the slow continuous rise of land thus brought about, the 

 permanence of continents is not so easily explained. 



The constant denudation by rain and rivers must inevitably lessen 

 the downward pressure which the land exerts on the upward force 

 that balances it, so that a rise must ensue, otherwise the equilibrium 

 between the two antagonistic forces could not be maintained. More- 

 over, some lateral movement or pressure from beneath the sea-bottom 

 towards the land would seem to be another necessary consequence, in 

 order to replace the mass of matter removed by denudation and to 

 make good the density lessened b)' the rise of land. 



liaised beaches seem to occiir all round Ireland, and Professor Hull 

 tells us (in his Physical Geology of that country, 2nd ed., p. 143) that on 

 following them from Antrim southward towards Dublin their elevation 

 is found to decrease from the north to the centre of Ireland. This 

 also is what might be expected, seeing that the rainfall decreases in 

 the same direction. It would be desirable, however, to test the 

 matter by observation on small islands, like the Azores and St. Helena, 

 far off from any coast. In such cases there should be little evidence 

 of recent raised beaches, although elevations of course might happen 

 from causes entirely different from those we have been considering. 



The continual accumulation of sediment brought down into the 

 ocean by rivers must augment the load upon the sea-bottom and cause 

 it to sink. This increase in the downward pressure, as already stated, 



' Jouru. Geol. Soc, Xovember, 1879, p. 810. 



