40 



EECEEATIYE SCIENCE. 



our "Walk beyond the immediate region of 

 Pevensey, we should see, in the railway-cut- 

 tings, the roadsides, and in the banks of 

 rivulets, that these sands, clays, and stones 

 succeed each other in regular and definite 

 order ; that one after the other they lead up 

 to the chalk-hills, under which they dip 

 downwards and disappear. Some of these 

 strata contain ammonites, or great ornamental 

 nautilus-like shells, sponges, palatal teeth 

 and scales of fishes, molluscs or shell-fish, 

 and other fossil marine objects, which mark 

 at once their ancient oceanic conditions; 

 others contain paludina;, or river- snails, gi- 

 gantic bones of extinct reptiles, plants, and 

 minute crustaceans {Cypridcn), the relics of 



Fig. 3.— Diagram of the Succession of Strata near 

 Pevensey. a. Tertiary drift ; h, c, d, beds of clialk 

 forming the downs ; e, upper greensand ; /, gault ; 

 g, sand and stone ; /), pyritous and ferruginous 

 beds; i, limestone (ragstone) — lower greensand; 

 A-, weald clay and sandstone; I, bank of beach 

 shutting in estuary; m, alluvial or marsh land. 

 The edges of the strata presented at the surface at 

 a, b, c, d, e, f, </, h, i, are the outcrops, or hassctting 

 edges. The direction-aiTow in the chalk (near c) 

 shows the dip of the strata. 



a vastly older estuary. Out of these mate- 

 rials, as out of the river-shells and oyster- 

 banks, the bones, leaves, and canoes of Peven- 

 sey levels, we can clearly read the history of 

 past events, and repeople the ancient lands 

 and seas with their ancient inhabitants. We 

 can tell the lines of the old coasts, the area 

 of shallow water, the estuary or river-delta, 

 the region of deep sea. All the evidence is 

 complete ; the relics so wonderfully preserved 

 to us throughout countless years — for these 

 surrounding cretaceous and wealden depo- 

 sits are of primeyal date, and belong even to 

 the middle period of geological history — are 

 as uncommingled and as faithfully indicative 

 of the ancient physical conditions with which 

 they were associated and connected. 



We can tell the strange kinds of trees and 

 plants which grew upon the old oolitic land 

 before it sank down under the chalky sea j we 

 can trace age by age the old sediments en- 

 croaching on the sinking land ; we can note 

 every cessation of its downward course ; we 

 can perceive the reversal of the movement, 

 and the sea-bottom uprising again as land, 

 every fresh ridge of the ocean's margin re- 

 ceding ever and anon from the wider and 

 wider extended soil, on which new forms of 

 plants and animals appear ; until we ap- 

 proach the age of Man, and find his traces, 

 too, and his records added to the ever- 

 changing scene. 



Looking backward into the abyss of time, 

 we see older and older of those sedimentary 

 formations — other lands and other seas of 

 still more vast antiquity. We peer into the 

 profundity of the past until we behold, in our 

 mental vision, only low insular specks of 

 gneissic rock ; the land's first boss-like crests 

 and crowns peeping above the waves and 

 dotting the wide expanse of an earth-covering 

 ocean, still warm, perhaps, and reeking with 

 the primeval central heat. And then— 



" One vast expanse of liquid green, 

 Ocean's self, breaks on the eye 

 In inexpressible majesty." 



Ever and ever, since the dry land first 

 appeared, has the sea been at its monotonous 

 toil; ever and ever murmuring, surging, un- 

 dermining, hurling down the earth, night and 

 day toUing and labouring. At work even in 

 its placid moods ; when, basking in the sun's 

 bright glittering rays, it lies quiescent with- 

 out a rufile on its polished face, with gently 

 heaving breast it idly chafes the pebbles of 

 the shore. 



Such is the ceaseless work of the sea, and 

 thus, through countless ages, have the rock- 

 strata of our earth been elaborated. 



S. J. Mackie. 



