rOOED — ON ENGLISH GEOLOGY AND GEOGEAPHY. 41 



the sea, is the effect produced by the enormous wasting power of 

 the waves. The whole line of the coast is deeply embayed, and 

 exhibits a series of projecting headlands or promontories. In some 

 places caves of considerable size have been formed at the base of 

 the cliff, hollowed out by the constantly wearing action of each tide. 

 These caves are apparently the cause of great masses of the chalk 

 giving way at the summit of the cliff; large boulders of chalk strew 

 the beach, and a flooring is formed in some places, by the consoM- 

 ation of these masses : in others the rock falls in, and makes an 

 inclined plane with the surface of the beach, sometimes ten or 

 fifteen feet in height. 



Almost the entire length of the coast at low water is strewn by 

 large boulders of chalk; locally termed **the rocks," extending 

 seawards for a distance of nearly a quarter of a mile ; quantities of 

 seaweed — fucus — and barnacles, adhere to these boulders, thereby 

 protecting them from the force of the breakers. 



On a closer inspection of the cliff, regular layers of flint are 

 seen in a horizontal position, at intervals of from four to six feet 

 apart, — parallel with the lines of stratification. Some of the layers 

 obliquely intersect the beds of chalk. The shape which the flints 

 assume is either tabular or rounded in the most fantastic forms, 

 having filled up cavities in the chalk, and taken the form of these 

 cavities. 



* '' The flat tabular flints, which are coincident with the 

 stratification, are of a different age from the similar layers which 

 are found filling cracks and joints. The former are contempor- 

 aneous with the chalk, and the flinty matter was deposited at the 

 same time as the chalky matrix ; the latter are, on the contrary, 

 of more recent date, having been formed by the percolation of 

 infiltrating water holding silica in solution, into cracks and joints 

 which were formed in the chalk, during or after its solidification." 



It may perhaps be needless to remark that chalk is nearly pure 

 carbonate of lime, and may therefore be considered an earthy 

 limestone. 



Mr. Henry Clifton Sorby (the distinguished Microscopist) , 

 from an examination of thin slices of chalk under a microscope, has 



*rroiii Catalogue of Museum of Practical Geology, 1863. 



