February, 1906.] 



KNOWLEDGE & SCIENTIFIC NEWS. 



349 



line towns, and with the present value of the land to be 

 salved there is little more to be expected. Mr. A. J. 

 Sruier has recently shown how useless it is tO' expect 

 much in the way of private enterprise. Takinjj an 

 acre of land tO' be worth ^25, or about i|d. a square 

 yard, and reckoning that for every lineal yard of coast 

 washed away eacli year twO' square yards are lost, 

 the total loss would be 2id. per yard of coast. Defence 

 works vary considerably in cost, but a fair average 

 works out at ;^i9 per yard of coast. Interest on this 

 at 2 J per cent, would amount toi 9s. 6d. a year, and 

 with this cost it would be possible tO' save per annum 

 twopence-halfpenny worth of coast. It is scarcely to 

 be expected that such an unremunerative expenditure 

 would be incurred either by private land-owners or b\ 

 the State itself. Only where the land in danger ac 

 quires a value in consequence of the growth of popula- 

 tion do defence works become of a remunerative nature. 



The causes of this denuding action of the sea are to 

 Ije found in purely geological considerations. Ever 

 since the time that this country rose for the last oc- 

 casion out of the sea, a sea covered with the delris of 

 the ice-sheet, which was then commencing tO' pass 

 away, she has been subjected to the battering-ram 

 action of the tides, and wave-action brought into plnv 

 thereby. 



There is a general agreement amongst geologists 

 that at the time of the uprise of the country from the 

 glacial sea, it rose to a somewhat greater height than 

 tfiat at which it now stands. The evidence on which 

 this IS based is formed for the most part in the exis- 

 tence of submerged forests in many parts of the coasts, 

 although on the face of it the existence of a single 

 buried forest is insufficient evidence on which to base an 

 opinion that the part in question at one time stood 

 higher than now. But taken as a whole it may be as- 

 sumed that England has been subjected, since the 

 growth of these post-glacial forests, to^ a subsiding 

 movement, and this has brought the areas in C|uestion 

 below the level of the sea. When that movement of 

 subsidence ceased, we have nothing to show. So far 

 as existing records show, we can only suspect a. move- 

 ment of subsidence in the historic period, but this lacks 

 positive proof. 



For the causes which have resulted during vcrv 

 many years in the gradual wastage of our coasts, we 

 must, therefore, look entirclv to marine and aerial de- 

 nudation, acting as a rule together. In the case of 

 dills having a much-jointed structure, or with verticil 

 and diagonal joints and fissures, aerial denudation is 

 as important a geological force as marine. The 

 chemical action of percolating rain in loosening the 

 constituents of some rocks, and the splitting action of 

 such waters under, the influence of frost, all tend to 

 degrade the face of a cliff, and the talc is taken up by 

 the tides, by whose action the disintregrated material 

 is borne away to sea. 



Rut in low-lying coast-lines, where the action of 

 frost is slight, or on those shores where, owing lO' the 

 nature of the material of the cliffs, chemical action is 

 almost entirely absent, there marine denudation is 

 wholly responsible for the loss of acres of land, and 

 where the shores are so' low as to be subject even but 

 rarely tO' flooding, the area covered is at once rendered 

 useless for agriculture, and so receives even less at- 

 tention than it formerlv had, in the direction of pro- 

 lection against the inroads of the sea. Thus, in the end, 

 it becomes permanently lowered by further denuda- 

 ti(>n, until its surface is beneath the le\el of the sea. 

 Hut marine (Iciuulalioii, siniplv, ni;iy be the cau.se of 



many a noble cliff crumbling away. It is estimated 

 that many of the prevalent storms which arise in the 

 .\orth Sea show their effects on our eastern and north- 

 east coast in waves which beat upon the cliffs with 

 a force varying between two to three tons to the square 

 foot. A change in the nature of the strata in a cliff, 

 owing to the strata dipping at an angle in a direction 

 parallel with the coast, will be sufficient for such 

 a force to find a suitable lodgement on which to play 

 with success. Or it may result in undermining, until 

 the upper parts of a horizontally stratified cliff may 

 project several feet beyond the base of the cliff. In 

 that case a period will be soon reached at which the 

 overhanging portion will fall. Then marine action, 

 which commenced the process by its undermining 

 action, will complete the work by bearing away 

 the fallen material, and rcdepositing it elsewhere. But 

 such redeposition seldom results in the formation of land 

 elsewhere. It mav shoal up a sea, but only to a certain 

 point. A\'ithout any subsequent submarine upheaval, 

 the debris of the land so denuded rarely results in dry 

 land. Without a counteracting uprise, the tendency 

 of the land is towards complete disappearance beneath 

 the sea. It is not alwavs realised that were the de- 



The Rai.sed Beach, showing Cave-like Holes (/>') where the Loose 

 Larger Stones at the top have fallen away. 



nudalion of the land to gO' fonvard unchecked, the 

 result would be the complete disappearance of our 

 land areas. In fact, so great is the preponderance of 

 sea-areas that were the earth completely spheroidal. 

 there would be a universal ocean two miles deep. For- 

 tunately, as geology teaches us, time after time the 

 results Of the degradation of the land have been ren- 

 dered nugaton,- by upheaval. 



But in our own country, at the present time, we have 

 no decisive evidence that either upheaval or subsidence 

 is going on. Denudation of our coasts proceeds with 

 no check placed upon it by natural cau.ses. It will be- 

 come a serious question as to whether artificial pro- 

 tection will not sooner or later become an imperative 

 n.itional concern. 



The last movement of upheaval which Ivngland under- 

 \\cnt was that which on our south coasts elevated the 

 raised beaches which .are there found, and even though 

 the existence of buried forests seems to show a sub- 



