{110} That the evidence of geology, as far as it goes, is favourable to the theory of descent is claimed in the _Origin_, Ed.
i. pp. 343-345, vi. pp. 490-492. For the reference to _net_ in the following sentence, see Note 1, p. 48, {Note 161} of this Essay.
Referring only to marine animals, which are obviously most likely to be preserved, they must live where sediment (of a kind favourable for preservation, not sand and pebble){111} is depositing quickly and over large area and must be thickly capped, littoral deposits: for otherwise denudation ,--they must live in a shallow s.p.a.ce which sediment will tend to fill up,--as movement is progress if soon brought up subject to denudation,--[if] as during subsidence favourable, accords with facts of European deposits{112}, but subsidence apt to destroy agents which produce sediment{113}.{111} See _Origin_, Ed. i. p. 288, vi. p. 422. "The remains that do become embedded, if in sand and gravel, will, when the beds are upraised, generally be dissolved by the percolation of rain-water."
{112} The position of the following is not clear:--"Think of immense differences in nature of European deposits,--without interposing new causes,--think of time required by present slow changes, to cause, on very same area, such diverse deposits, iron-sand, chalk, sand, coral, clay!"
{113} The paragraph which ends here is difficult to interpret. In spite of obscurity it is easy to recognize the general resemblance to the discussion on the importance of subsidence given in the _Origin_, Ed. i. pp. 290 et seq., vi. pp. 422 et seq.
I believe safely inferred groups of marine fossils only preserved for future ages where sediment goes on long and with rapid but not too rapid deposition in these contingencies be going on? Hence in past ages mere [gaps]pages preserved{114}. Lyell"s doctrine carried to extreme,--we shall understand difficulty if it be asked:--what chance of series of gradation between cattle by at age as far back as Miocene{115}? We know then cattle existed. Compare number of living,--immense duration of each period,--fewness of fossils.{114} See Note 3, p. 27.
{115} Compare _Origin_, Ed. i. p. 298, vi. p. 437. "We shall, perhaps, best perceive the improbability of our being enabled to connect species by numerous, fine, intermediate, fossil links, by asking ourselves whether, for instance, geologists at some future period will be able to prove that our different breeds of cattle, sheep, horses, and dogs have descended from a single stock or from several aboriginal stocks."
This only refers to consecutiveness of history of organisms of each formation.
The foregoing argument will show firstly, that formations are distinct merely from want of fossils , and secondly, that each formation is full of gaps, has been advanced to account for _fewness_ of _preserved_ organisms compared to what have lived on the world. The very same argument explains why in older formations the organisms appear to come on and disappear suddenly,--but in [later]tertiary not quite suddenly{116}, in later tertiary gradually,--becoming rare and disappearing,--some have disappeared within man"s time. It is obvious that our theory requires gradual and nearly uniform introduction, possibly more sudden extermination,--subsidence of continent of Australia &c., &c.
{116} The sudden appearance of groups of allied species in the lowest known fossiliferous strata is discussed in the _Origin_, Ed.
i. p. 306, vi. p. 446. The gradual appearance in the later strata occurs in the _Origin_, Ed. i. p. 312, vi. p. 453.
Our theory requires that the first form which existed of each of the great divisions would present points intermediate between existing ones, but immensely different. Most geologists believe Silurian{117} fossils are those which first existed in the whole world, not those which have chanced to be the oldest not destroyed,--or the first which existed in profoundly deep seas in progress of conversion from sea to land: if they are first they give up. Not so Hutton or Lyell: if first reptile{118} of Red Sandstone really was first which existed: if Pachyderm{119} of Paris was first which existed: fish of Devonian: dragon fly of Lias: for we cannot suppose them the progenitors: they agree too closely with existing divisions. But geologists consider Europe as a pa.s.sage from sea to island to continent (except Wealden, see Lyell). These animals therefore, I consider then mere introduction from continents long since submerged.
{117} Compare _Origin_, Ed. i. p. 307, vi. p. 448.
{118} I have interpreted as _Sandstone_ a scrawl which I first read as _Sea_; I have done so at the suggestion of Professor Judd, who points out that "footprints in the red sandstone were known at that time, and geologists were not then particular to distinguish between Amphibians and Reptiles."
{119} This refers to Cuvier"s discovery of _Palaeotherium_ &c. at Montmartre.
Finally, if views of some geologists be correct, my theory must be given up. [Lyell"s views, as far as they go, are in _favour_, but they go so little in favour, and so much more is required, that it may viewed as objection.] If geology present us with mere pages in chapters, towards end of