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 a velocity has been imparted to the fragments discharged exceeding twice that which can be produced by artillery. And yet, as we have shown, we should require a velocity many times as great as that which our mightiest cannons can generate, if the missile so discharged were to be carried free from the earth altogether. No doubt the inadequacy of our present volcanoes is a very great difficulty in the acceptance of the terrestrial theory of meteorites. But the improbability that meteorites should have so sprung appears to me to be very much less than the improbabilities which accompany the supposition that the origin of these bodies can be explained in any of the other ways which have been proposed. It seems therefore necessary to submit this notion of the terrestrial origin to an extremely close scrutiny, and see how far the objections that may be urged against it can be overcome.

I am quite aware that able geologists have maintained that there is no stratigraphical evidence to show that volcanoes of early geological times were more potent than those of the present day. But in so far as such evidence may be wanting I think we can only attribute it to that imperfection of the geological record which has been so often invoked to account for the absence of direct testimony in support of conclusions which there are good theoretical reasons for entertaining. It would seem that the present case is one in which the absence of direct testimony need not greatly concern us. The laws of cooling are not to be impugned, and those laws of cooling declare with unfaltering logic that the thermal conditions to which volcanoes owe their origin must have been such as to make volcanoes far more potent in primeval times while the earth was still young than they are at present.