Seite - 344 - in The Origin of Species

314 ORIGIN OF SPECIES age, was deposited during a c?.*:i.-ird cscfZsr:!?:: of and ditts gained ctmsiderakie thirkness. An geologica] facts tell ns plaiohr that each 3.rt3. -3^ under- gonenameroas 5lo"w osciilations of level, and ^.r^Mrentlv these oscillaticHis bave asected wide spaces. Coaisectienthr, foraaft- tions rich in fossils and sofBaently thick and extensile to resist snhsequient degradaticm, will have been :£cKined otO" wule spaces dnring periods ci subsidence, bet only wirere tiie supply of sediment was sufficient to keep the sea sbaDow and to embed and preserve the resnains before tfaey had time to decay. On die other hand, as l(Xig as the bed of the sea remains stationary, tkick deports cannot have been accnoni- tated in the shallow parts, which are the most favoarafaie to Hfe. Still less can this have ha£^>ened cfaning the ahemate periods of elevation: or, to speak more accnratdy, tfse be<^ which "w^re then acctmmlated will geaerally have beoi de- stroved bv being C5)raised and toongfat within the famits of the coast-action. These remarks apply chieSy to Uttoral and snb-Iittoral de- posits. In the case of an extensive and^bDow sea, snch as that within a large part of the Malay .\rchipelago, where the depdi varies from 30 or 40 to 60 fathcHns, a wid>dT extended formation might be formed dnring a period of deration, and yet not suffer excessively from denodation daring its slow iq^ieaval; bat the thickness of the formation could not be great, fcr owing to the elevarory movemsit it wookl be less than the depth in which it was formed: norwould the deposit be much consolidated, nor be capped by overlying formatiaasy so that it wcnli rm a good chance of being worn away by atmospheric degradation and by the action of the sea during subsequent oscillaticns of leveL It has. however, been sug- gested by Mr. Hopkins, that if one part of the area, after rising and before being denuded. subsMied. the deposit formed dtrrins^ the rising movement, thoogfa not thick, might after- wards become protectef '" " ""esh accumulatioas. and thus be preserved for a longper Mr. Hopkins also expresses his belief that sedmtentarj beds of considerable horizontal extent have r^- ' tij destroyed. Bet all geologists, excepting _; :. "^ that our present metamorphic schists and pltttomc r . -.- :ice