Miss Eyton — On Glacio-Marine Denudation. 547 



large granite and limestone boulders, which, are scattered at different 

 levels over the surface of the land. And this is easily accounted for 

 when we consider that, during the succeeding period of submergence, 

 all the lighter material would be washed away by the waves, to re- 

 appear in the form of marine drift, the heavy boulders alone remain- 

 ing in, or near, their original sites. 



It is, however, certain, that if the Tern basin was originally 

 excavated by ice, the sea must, at least, have done much towards 

 shaping and modifying its outline. To the eye of a geologist, look- 

 ing from the centre of the depression above alluded to, it is easy to 

 re-picture the time when the whole of the surrounding country, with 

 its rich pastures, its towns and rural homesteads, and its busy work- 

 ing population, was a vast bay or inland sea, resembling the Irish 

 Loughs of the present day, having its outlet into the Severn sea at 

 the northern extremity between the two before mentioned basaltic 

 barriers. The coast line, though not in all places equally distinct, 

 may yet be traced almost continuously ; and nowhere more clearly 

 than in the terrace of Haughmond Hill. Had the denudation of the 

 Sandstone been entirely effected in this locality by ice, it would have 

 left its marks, in the shape of furrows and striae, upon the hill-side ; 

 but none such exist. On the contrary, the hill forms a terrace ex- 

 tending in a direct line, with smooth and rounded outlines, such as 

 could only have been formed by the continuous and gradual action of 

 the waves, wearing away the softer rock which then concealed the 

 face of the hill, leaving bare the basaltic ridge. The same obser- 

 vations apply wherever trap intrusions occur, as at Lilleshall and 

 Wrockardine Hill. 



But it is in the Drifts that we find the strongest evidence of the 

 sea's presence. The lowest of these consists of a bed of loose 

 coarse-grained sand, partially filling up the hollows over nearly the 

 whole extent of the basin, and sometimes appearing upon the sides 

 and summits of the lower elevations. I infer that this bed is of 

 marine origin, since the uniform action of the sea could alone have 

 distributed it so evenly and generally over so large a surface. 

 When microscopically examined it is found not to consist chiefly of 

 the denuded sandstone, but of minute rounded fragments of quartz, 

 syenite, and greenstone. It has not hitherto yielded any organic 

 remains. 



Eeposing conformably upon this, and extending along the base of 

 the Wrekin chain, and of the Carboniferous hills, is a line of marine 

 drift clearly indicating an old sea-board. This drift consists of 

 clay, mixed with rounded shingle, slightly bedded. An admirable 

 section is exposed to view in the clay -pit worked by Mr. More, of 

 Ketley Brook. The face of the bank, which is here rather steep, 

 has been cut away, so that the position of the beds, shingly-clay resting 

 upon sand, is visible. A curious sub-atmosjoheric effect occurs here, 

 which, although foreign to the present subject, is so remarkable as 

 to be worth mentioning. The rain, penetrating the upper bed, has 

 formed small streams trickling through into the sand, and carrjdng 

 particles of the clay with it, to which the sand adhering, columnar 



