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June 24th /56/

It is likely some stages will be fd. beneath lowest Silurian, even Barrandes strata named primordial not to the other day are now apparently underlaid. But yet view advanced is this work, seeing in what force different classes, with most diverse forms, seem to start into life in Silurian lowest rocks. We cannot account for disappearance of the imagined piles of formations (probably exceeding manifold all between Silurian & present day) by metamorphism or denudation, for Palæozoic Silurian strata are yet the widest spread & very often quite unaltered. Looking to our continents of Europe, & N. America, & with less but some evidence even to S. Africa. S. America & Australia, we see since oldest deposits that these areas, have many times sunk & many times elevated, gives rise to sediment & resunk & reelevated. But yet even during this period of greatest subsidence, such as

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to 15,000 ft during Silurian & 10,000 ft during carboniferous, & great subsidence of trias, we have evidence in the very sediment that land was somewhere not very far off. Sometimes littoral shells, sometimes plants which it seems cannot float far. Hence I shd conclude our continents with vast retractions & yet vast expansions have existed since Silurian. Look to our oceans; first view probable that continent has sunk over these areas, but I doubt whether any direct evidence, volcanic, coral islds & fringes of tertiary strata. I know of no good reason to suppose that continents ever existed where our great oceans extend. Not a fragment of Palæozoic or secondary rock has ever been fd. on an isle 1000 miles from a continent. But has

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I may say that I can imagine in course of whole periods, that all our continents will disappear, that new continents are formed where oceans now extend.

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this state of things endured since first [observant] of world. We are profoundly ignorant. But let us imagine that in course of cycles of not ages, but great periods, those unknown laws by which earths crust is carried & depressed, do change then place of action, & a great continent shd be formed, in mid Pacific, or mid S. Atlantic, or mid Antarctic ocean then we shd hence have land there now without one parent continent were to sink. But why shd all sink? I shd think continent in mid ocean wd be formed most slowly, the elevating movement being aided only by volcanic outburst & lime secreted from water by animals. Would a new continent by balancement necessitate a corresponding sinking elsewhere?

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Put the case briefly thus, I can imagine that in long course of ages where our continents stand there may be some dry ocean - & in our ocean continent; but if so, judging from present enormous times required, for these show our continent have been continents since Silurian. X But it may be said that where our ocean now stand there lie Silurian & Secondary submerged rocks which cd be brought up. But of this no evidence, no fragment of Palæozoic rock or Secondary fd. - X A new continent cd be formed very slowly volcanic outburst & calc. matter, for we see how great a part of existing continents sedimentary rocks make. Thus I can imagine all our sedimentary rocks might be lost; but this is idle conjecture.