Or, let us take the Brachiopods. These have a bivalve shell, the parts of which, however, are not pulled apart after death, and only need to open a little way even in life to admit the sea water which brings them their food. Yet, though the valves do not gape after death, there is when dead and empty a =hole= at the hinge or beak, which would readily admit mud if such were present in the water, or if the shells after death were subject to the ordinary movements of tide, wave and current. Yet Dawson[63] says of the Brachiopods, Spirifer and Athyris: "I may mention here that in all the Carboniferous limestones of Nova Scotia the shells of this family are usually found with the valves closed and =the interior often hollow=." Of course he tries to explain how this state of things might occur "in deep and clear water"--for some of the modern species are found in the clear depths 18,000 feet down--and he thinks that their entombment in this condition "does not prove that the death of the animals was sudden." But we now know that there is no means of producing a stratified formation in this "deep and clear water," and hence that some revolution of nature is implied by the conditions in which we find them. Some people seem to have converted David Hume's famous sentence into a scientific formula, thus: "Anything contrary to Uniformity is impossible: hence no amount of evidence can prove anything contrary to Uniformity." For the trouble in this case is that, not only do such conditions prevail "in all the Carboniferous limestones of Nova Scotia," which must be several thousands of square miles in extent, but in the Devonian shales and Silurian limestones of Ontario and the Middle States at least--perhaps over the rest of the world--the Brachiopods are found =in this same tell-tale condition=, and it would establish a very dangerous precedent to admit abnormal conditions in even a single case. I have only touched upon the voluminous evidence that might be adduced in the case of the lower forms of life. Had I the space, I might show how the marvelously preserved plants of the coal beds tell the same story. But we must pass on to consider the remains of the larger land animals. I have already given a quotation from Dana about the mammoth and rhinoceros in Northern Siberia, where he says that their encasing in ice and the perfect preservation of their flesh "shows that the cold finally became =suddenly= extreme, as of a single winter's night, and knew no relenting afterward." Not very many serious attempts have been made to account for this remarkable state of things, which is a protest against uniformity that can be appreciated by a child, and I never heard of any theory which attempted to account for the facts without some kind of awful catastrophe.