128 



RECREATIVE SCIENCE. 



What, then, has cast them up thus in Alum 

 BayP 



Some time since, I was engaged in map- 

 ping out the fissures in the British Channel — 

 for that narrow sea is but the result of frac- 

 ture, from an upburst which rent a valley 

 through the white chalk -beds that form the 

 lofty cliffs on either side. By marking the 

 lines of greatest sea-depth in fathoms, the lines 

 of fracturage became easily perceptible until 

 we got opposite to the Isle of Wight. There 

 depths, equal to any we had found in the pro- 

 per lines of cracks, seemed disposed in aU 

 sorts of ways, or, rather, one might say not 

 disposed at all. By dint of perseverance, 

 however, something of a star-like figure was 

 made o\it, marking, to the eye of a geologist, 

 a point of uplift or centre of disturbance. 

 On pointing this out to a friend, I was 

 told that a boss of granite existed in the sub- 

 marine depths there; and in this, at once, 

 we seemed to have the cause and explanation 

 of the stratal phenomena of Alum and Fresh- 

 water Bays — the source and origin of the 

 force or power which had cast on end the 

 sea-girt cliffs of lovely Vectis long before 

 the legions of imperial Home had seen or 

 named the pretty isle. 



A few words now about the " Needles." 

 Nature is a curious carver, and models 

 strange things. The sea also does many 

 remarkable things in its multiform toil ; the 

 air, with its indefatigable assistants, wind, 

 rain, frost, and snow, produces great results 

 by scarcely perceptible means. 



Those curious pinnacles, like as the moth 

 endured a chrysalis condition ere it assumed 

 its winged state, have been something else 

 before they were "Needles." What they 

 were we see evidence of in the neighbouring 

 coves and bays j we see also on the other 

 side of the "narrow straits" at Etretat, 

 Fecamp, and Dieppe. 



First the sea slightly undermines the 

 chalk-beds of the cliffs its ravages have 

 worked into steep and narrow promontories, 



and then tide after tide moistens it high up 

 with its spray.* When winter frosts set in, 

 the icy cold seizes vitally, as one might say, 

 on the damp rock, and with its ex ansive 



Fig. 3.— Ideal Section of Promontory of Chalk, in the 

 first stage of waste, showing a block broken out by 

 frost, -which, on falling, will form a step or under- 

 cut.* 



power splits off some fragments, which, when 

 the thaw releases them, fall down and goon 

 become the prey of boisterous waves, or yield 



l^iQ. 4_ — Ideal Section of Chalk Promontory, sliowing 

 a series of blocks broken out by the frost.* 



up their substance in tiny particles to sum- 

 mer's dancing ripples. 



For century after century, the frost con- 

 tinues its periodic exerci3e,hurling down, year 



* The boring molluscs, such as the Saxicave, may 

 also assist in working out the first steps in the face 

 of the chalk-cliifs ; but the frost is the great and con- 

 tinuous agent. 



