574 Correspondence. 



sea-cliffs, most of which do not apply to the escarpments with which 

 I am acquainted. I have only space for a few comiter-statements. 



1. The bottom of an escarpment does often keep to one level, and the top is 

 often uneven. 



2. Sea-cliflfs do not always run straight through homogeneous rocks, but very often 

 ■wind about in a succession of small capes and coves, which are included in "curves 

 of large radius." 



3. Among Archipelagos, such as the South of England must once have been, coasts 

 are as often beaehless as are the foot of escarpments. Shores suddenly sloping into 

 deep seas, at a stationary level, or any kind of shores continuously rising, could never 

 become covered with rounded shingle. 



4. Sea-cliifs are not " backed by higher ground " in many parts of Archipelagos. 

 Escarpments are often backed by higher ground. 



Destruction of Sea-cliffs. — What Mr. Whitaker says about the 

 atmosphere assisting the sea reads like special pleading for a 

 favourite agent. It is as obvious that the sea makes its cliffs as it is 

 that without the sea there would be no cliffs. At least two-thirds 

 of the downfalling is the result of sheer gravitation through under- 

 mining. Many sea-cliffs for ages stand at the angle of gravitational 

 repose. But as Mr. Whitaker admits that an immensely greater 

 quantity of rock is denuded by the sea than by the atmosphere, it is 

 not necessary that the relative claims of "the organ and the blower" 

 should in this case be applied. The fact that the atmosphere does 

 wear down and destroy sea-cliffs does not, however, seem quite 

 compatible with the theory which assigns to the atmosphere a power 

 of forming cliffs or escarpments. 



Preservation of Ice-marks. — Mr. Whitaker attributes a deficiency 

 of reasoning power to his opponents, while he himself uses one 

 kind of reasoning in speaking of the sea, and another in reference 

 to the atmosphere. If the preservation of glacial striee under the 

 sea, in some parts of the fjords of Norway, be an evidence against 

 sea-action, their perpetuation on rock surfaces under the air must 

 afford an equal proof of the inefficiency of rain. As regards the 

 latter, it should be remembered that they often extend over great 

 areas under a covering of soil, which could not be the case if " soil 

 is rotted subsoil " (as Col. Greenwood calls it) on its way to a lower 

 level. 



Professor Jukes on the Avon Gorge. — ^In your Magazine (Oct., 1867,) 

 this able geologist applies the " hard gorge and soft valley," theory 

 of Col. Greenwood, to the neighbourhood of Bristol. But from his 

 explanation, it is obvious that the theory requires the assistance of a 

 sliding scale to make it fit different localities. Besides the Clifton 

 gorge and the Bristol basin, there are at least ten hard gorges leading 

 out of soft valleys (some of them perfectly flat-bottomed plains, 

 with level -based escarpments, for instance, near Keynsham), which, 

 from the relative nature of the rocks in which they occur, would 

 appear to be inexplicable on the above theory. It may likewise be 

 asked, if the limestone on both sides of the Clifton gorge escaped 

 pluvial disintegration through being covered with newer rocks, how 

 were the limestone ridges of the Western Mendips preserved, in 

 Palaeozoic times, when the Old Eed Sandstone was in course of being 



