38 



EECEEATIVE SCIENCE. 



stout, broad wall unto this very hour, lias 

 tlie great change in the physical and geogra- 

 phical characters of Pevensey levels been 

 progressing. Unceasing, unvarying in its 

 process, has been the alteration of the tract 

 around those ancient castle-walls. The winds 



Fig. 1. — Diagrammatical Section of a Chalk-cliff, 

 showing the waste of land and the sorting of the 

 materials by the sea. a, Fallen masses of chalk- 

 rock ; 6,' flints left on the shore by the washing 

 away of the soft chalk, and forming a beach along 

 the level of high tide ; c, finer fragments, or sand, 

 deposited in the tidal zone, between high and low 

 water ; d, very fine earthy particles, or mud, depo- 

 sited under water. 



driving along the shore, by means of the 

 boisterous waves, the flint-shingle, derived 

 from the abrasion of the cliffs of Beachy 

 Head, first formed a tongue-like bar, the point 

 of which, ever creeping onward with the ac- 

 cumulation of each succeeding tide, gradually 

 shut in the estuary, which then, by means of 

 the river continuously bringing down fine 

 particles of mud, powdered by the ro-'n and 

 weather, from the surrounding hUls anCi lands, 

 in the lapse of time has been completely silted 

 up. Thus has been changed the whole 

 face of the district, and sheep and cattle 

 graze on verdant pastures that have sup- 

 planted the brackish waters of the indented 

 bay. In the mud, sand, and gravel strewn 

 .over this great plain, river-shells, bones of 

 wolves and other beasts, of porpoises and 

 fish, xjockle and oyster-shells, ancient canoes, 

 and bones of domesticated animals remain 



embedded, with the leaves and stems of hazel, 

 birch, oak, and other of the indigenous trees of 

 the ancient forests. 



Such are not, however, confusedly com- 

 mingled, but the bones and larger dehris are 

 deposited in one place, the shells and finer 

 sediment in another ; the calcareous shells of 

 the lymnseans are found still in the old river- 

 course, the oyster-beds at the former river- 

 mouths — all have been buried upon the spots 

 on which they lived or grew. The bones and 

 the canoes are where the currents, according 

 to their force and strength, deposited them, 

 affording thus clear evidence of the succes- 

 sion of the prominent events which have oc- 

 curred during the progress of the natural 

 operations instrumental in filling up the 

 ancient bay. 



Just as the history of the old castle itself 

 has to be made out from the study of its 

 masonry and its varied styles of architecture 

 — just as we have to test the knowledge de- 

 rived from the correlative sources of history, 

 old deeds, legendary tales, and traditions, by 

 the indicative characters of its actual struc- 

 ture ; so, in the study of the past history of 

 the physical conditions of any portion, how- 

 ever limited, of the dry land of our globe, 

 we have to measure all the other corroborative 

 or extraneous evidences by the standard of 

 the conditions of the strata, or beds of mineral 

 matter themselves. As the marks of the 

 mason's chisel or the trowel are in archaeo- 

 logical inquiries valuable indications of the 

 national workman by whose hands they were 

 made, so, too, the position of a shell in the 

 consolidated silt, the fragmentary op perfect 

 condition of a bone, and many other ap- 

 parently trifling features, have significations 

 and values of high importance in geological 

 or physical investigations. 



And the rock-strata of the earth are the 

 consolidated muds, sands, and beaches of 

 other shores and other ages — their fossils 

 the petrified remains of the shell-fish, plants, 

 or beasts, that existed on them or the adjacent 



