126 On Lines of Ancient Sea-Levels. 



pression of the land as any which exist on the shores of Scania, 

 where a great subsidence has been established, it must also 

 be borne in mind, that the rocky western coast of our island 

 offers equal signs of depression, since Cornwall and Pembroke- 

 shire, and even Cardigan, so near to the point of intense eleva- 

 tion, Snowdon, have each their submerged forests as well as 

 Lincolnshire. Examined, then, as a whole, England offers 

 many evidences which to me seem conclusive, that within a 

 very recent period, the land has undergone great and unequal 

 movements, both of elevation and depression, in relation to 

 the level of the sea. Scotland and Ireland present like pheno- 

 mena. In the latter country modern marine shells have been 

 found in many localities at various altitudes. .Scotland so 

 rich in superficial accumulations, also offers near her shores 

 many testimonies of former sea-bottoms laden with numerous 

 shells, but hitherto these remains have only been found at 

 comparatively low altitudes. Another class of detritus, in 

 which, in common with England, she is rich, consists of ex- 

 tensive irregular accumulations of clay, boulders and gravel, 

 usually called '^ till," and which may be compared with the 

 drift of the tract extending from Bedfordshire and the eastern 

 side of Huntingdonshire, to the coasts of Norfolk, Suffolk, and 

 Essex. A third class is composed of gravel and sand, often 

 arranged in terraces, which in some cases occur at different 

 levels, following the sinuosities of the bays and headlands of 

 the sea-coast ; in others ramifying into the interior, along the 

 sides of deep cavities occupied by fresh-water lakes. 



The well-known " parallel roads" of Lochaber offer the 

 most striking example of terraces at different levels above a 

 series of existing lakes, and their explanation has been long 

 the subject of controversy. For many years it was the favourite 

 hypothesis, based, however, upon the supposition of th-eiv per- 

 fect parallelism, that these lines of shingle were the shore lines 

 of the lakes when they stood at higher levels, from which they 

 have been successively let off by the breaking down or wear- 

 ing away of their barriers. Though supported by several good 

 observers, this view has always presented great difficulties as 

 to the demand upon our belief in the wearing away and de- 

 struction of enormous barriers. Very recently, indeed, the 



