Now, although there is nothing in my works to warrant the building up of continents in the Atlantic and Pacific even since the Eocene period, yet, as some of the rocks in the central Alps are in part Eocene, I begin to think that all continents and oceans may be chiefly, if not all, post-Eocene, and Dana's "Atlantic Ocean" of the Lower Silurian is childish (see the Anniversary Address, 1856). (47/4. Probably Dana's Anniversary Address to the "American Association for the Advancement of Science," published in the "Proceedings" 1856.) But how far you are at liberty to call up continents from "the vasty deep" as often as you want to convey a Helix from the United States to Europe in Miocene or Pliocene periods is a question; for the ocean is getting deeper of late, and Haughton says the mean depth is eleven miles! by his late paper on tides. (47/5. "On the Depth of the Sea deducible from Tidal Observations" ("Proc. Irish Acad." Volume VI., page 354, 1853-54).) I shall be surprised if this turns out true by soundings. I thought your mind was expanding so much in regard to time that you would have been going ahead in regard to the possibility of mountain-chains being created in a fraction of the period required to convert a swan into a goose, or vice versa. Nine feet did the Rimutaka chain of New Zealand gain in height in January, 1855, and a great earthquake has occurred in New Zealand every seven years for half a century nearly. The "Washingtonia" (Californian conifer) (47/6. Washingtonia, or Wellingtonia, better known as Sequoia. Asa Gray, writing in 1872, states his belief that "no Sequoia now alive can sensibly antedate the Christian era" ("Scientific Papers," II., page 144).) lately exhibited was four thousand years old, so that one individual might see a chain of hills rise, and rise with it, much [more] a species--and those islands which J. Hooker describes as covered with New Zealand plants three hundred (?) miles to the N.E. (?) of New Zealand may have been separated from the mainland two or three or four generations of Washingtonia ago. If the identity of the land-shells of all the hundreds of British Isles be owing to their having been united since the Glacial period, and the discordance, almost total, of the shells of Porto Santo and Madeira be owing to their having been separated [during] all the newer and possibly older Pliocene periods, then it gives us a conception of time which will aid you much in your conversion of species, if immensity of time will do all you require; for the Glacial period is thus shown, as we might have anticipated, to be contemptible in duration or in distance from us, as compared to the older Pliocene, let alone the Miocene, when our contemporary species were, though in a minority, already beginning to flourish.