APPEi^Bix. 355 



Appendix. — To help any one who may investigate the subject, I add a 

 notice of two points which at first struck me as difficulties in the way of the 

 atmospheric origin of these escarpments. 



1. The gi-eat spread of dipslope covered by a limestone at Great Baving- 

 ton only three feet and a half to four feet thick. No less than half a mile's 

 breadth of this limestone's outcrop is exposed, and it may seem that on the 

 atmospheric theory it must have melted away. But is the preservation of 

 this thin sheet any whit more easily accounted for upon any other theory ? 

 Could the glaciers have more easily ploughed out large bodies of strata in 

 the neighbourhood and left it? Could the seaV It is rather surprising on 

 any theory, but the following considerations may help to an explanation. 

 1st— The strata between this and the next overlying limestone — some forty 

 feet thick — are almost entirely shale and have easily been worked back from 

 it. 2nd— It overlies the whinsill, with only about a foot of shale between, 

 and, if I recollect aright, has a finely crystalline structure ; crystallised car- 

 bonate of lime is less liable to solution than ordinary limestone. The feature 

 of this limestone has a curved front — the only case I have noticed, (see p. 

 321.) 



2. Some sandstone crags— Queen's Crag in particular, have wasted at a 

 I'ate that instead of raising them into prominence above their line of escarp- 

 ment, ought to have made them bury themselves in the ground. The main 

 part of Queen's Crag has worked itself back into a recess, and its debris, 

 consisting of slices the whole depth of the seamless bed, cannot cover up its 

 front, and check denudation as smaller materials might. If this were the 

 usual mode of action, crags, on the atmospheric theory, could only get 

 their head above the surface to the height of the slicing bed. I believe this 

 difficulty disai)pears when the variable bedding of the sandstones is consi- 

 dered. Massive beds are of no great extent, quickly losing their massive 

 character when traced out. It is possible therefore that denudation has 

 brought the Queen's, and certain other, crags to a "measure" of rock that 

 will soon be worked out, aiul give place to a kind less open to wholesale 

 destruction. 



