_human_ cast and character of the contrivances which they exemplified. Not only could I understand the principles on which they were constructed, but further, not a few of them had, I found, been actually introduced into works of human invention ages ere they were discovered in the rock. What the great Creator-worker had originated in the Palæozoic and Secondary periods, had been in after times originated by the little creature-worker, wholly unaware that his contrivance had been anticipated, and was but a repetition of a previously executed design. In the later geologic ages the organization of the various extinct animals so nearly resembled that of the animals which still live, that we may regard it as not inadequately represented by the illustrations of Paley. A few such exceptional contrivances appear among the mammals of the Tertiary as that formed by the huge pickaxe-like tusks of the Dinotherium, or a few such extraordinary modifications of the ordinary mammalian framework as that exhibited in the enormously massive pelvic arches and hinder limbs of the Mylodon and Megatherium. But not until we pass into the deposits of the Secondary period, and get among its cephalopoda, do we find a mechanism altogether unlike any with which we are acquainted among living organisms. As admirably shown by Buckland, the partitions which separate into chambers all the whorls of the ammonite except the outermost one, were exquisitely adapted to strengthen, by the tortuous windings of their outer edges, a shell which had to combine great lightness with great powers of resistance. Itself a continuous arch throughout, it was supported by a series of continuous arches inside, somewhat resembling in form the groined ribs of the Gothic roof, but which, unlike the ponderous stone work of the mediæval architects, were as light as they were strong. And to this combination of arches there was added, in the ribs and grooves of the shell, yet another element of strength,--that which has of late been introduced into iron roofs, which, by means of their corrugations,--ribs and grooves like those of the ammonite,--are made to span over wide spaces, without the support of beams or rafters. Still more recently, the same principle has been introduced into metallic boats, which, when corrugated, like the old ammonites, are found to be sufficiently strong to resist almost any degree of pressure without the wonted addition of an interior framework. Similar evidences of design appear in the other extinct molluscs peculiar to these geologic ages, such as the hamite and turrilite. The belemnite seems to have united the principle of the float to that of the sinker, as we see both united in some of our modern life boats, which are steadied on their keel by one principle, and preserved from foundering by the other; or as we find them united by the boy in his mimic smack, which he hollows out and decks, in order to render it sufficiently light, while at the same time he furnishes it