128 Reviews — AppacJis Julius Ccesar's Landing in Britain. 



and that the sea flowed over what is now marsh land, he supposes 

 that the rising tide carried sediment into the bay, and deposited 

 it behind the island ; thus gradually silting up this part of the bay. 

 At the same time, by the eddy in the bay, silt would be deposited on 

 the south-west of the island, the main stream at low water flowing 

 out between these shoals. The old island of Komney gradually 

 extending northwards, towards the coast of Kent, finally shut out 

 the waters there entirely ; but the western shoal never quite 

 reached the mainland, and there has always been a channel on its 

 western side, where the Eother now runs. 



The foregoing is a very bald sketch of Mr. Appach's views, in 

 support of which he quotes from previous writers. His own ob- 

 servations are numerous, and this part of the volume forms a useful 

 contribution to Geological literature. 



It will be seen that Mr. Appach differs materially from those who 

 regard Eomney Marsh wholly as the delta of the Eother, and he 

 aptly remarks that whilst deltas invariably have an inclination 

 from the land towards the sea, marshes formed by the sea, as 

 Eomney Marsh, slope inwards towards the land (p. 24). Of course 

 it would not be denied that the sediment brought down by the 

 Eother has greatly aided in silting up the area. In Mr. Appach's 

 supposition regarding the earlier stages in the formation of 

 the Marsh, with the formation of shoals, and the gradual de- 

 position of silt around them, he does not much differ from 

 opinions which have been published before, but his account of 

 subsequent events departs somewhat from the common explanation. 

 Thus by the gradual extension of the eastern island (Eomney) 

 landwards, the sea was shut out on the east side, and the water 

 at ebb tide drained west and south-west into the main channel 

 between the islands. Mr. Elliott^ holds that whilst the Eiver 

 Limen never ran out at Lympne along the north side of the 

 marsh, yet that the backwater scoured along a channel here, 

 forming the ancient harbour of Lympne, and that this channel 

 gradually silted up. The common belief is that the Eiver Limen 

 itself occupied this channel until its course was altered to Eomney. 

 The present appearance of the marshes gives but little evidence 

 upon this question. There is no trace of the supposed river course 

 west of Lympne, whilst that to Eomney is still plainly traceable. 



The French coast has undergone fewer changes ; but such as 

 have occurred are not unimportant. The chief agent in change has 

 been " blown sand," which has, more or less, choked up the river 

 mouths ; the harbour of Boulogne being even now kept open with 

 difficulty. We may here note a Geological error into which Mr. 

 Appach has fallen in regarding the cliffs north and south of 

 Boulogne as being composed of Wealden Eocks. They consist of 

 Portland and Kimmeridge Beds, with only occasional thin patches 

 of Wealden on their summits. 



In conclusion, we may briefly note the historical application 



1 '■'• Account of the Dymcliurch "Wall." Proc. Inst. Civ. Eng., vol. vi. p. 467, 

 1847. Appendix to C. R. Smith's Eeport on Lynme, 4to., 1852, p. 41. 



