The passing years have brought to us more complete knowledge of these strange beasts–now classed as the "Dinosauria"–and new kinds and complete skeletons of those already known have been discovered in the United States and in Belgium. The leg bones and vertebræ of one of the biggest were found near Oxford, and are in the Oxford Museum; it received the name Cetiosaurus. Only a few years ago a very complete skeleton of a creature closely allied to Cetiosaurus was with great labour and skill dug out of the Jurassic rocks of Wyoming, U.S.A., by Dr. Holland, at the charges of Mr. Andrew Carnegie. It was known as Diplodocus (referring to certain bones in its tail), and a wonderful cast of the completely reconstructed skeleton was presented to the Natural History Museum in London, when I was Director, by Mr. Carnegie. The skeleton is 84 ft. long; but we must not be mis-led as to the animal's actual bulk by this measurement, for the tail is 46 ft. long and whip-like, whilst the neck is 23 ft. long and carries a small head not bigger than that of a cart-horse. The jaws were provided with small peg-like teeth, showing that the beast fed on soft vegetable matter. The body, apart from neck and tail, was really only a little bigger than that of a large elephant, and the limb-bones longer in the proportion of about six to five. Another reptile very similar to these and also found in the mesozoic rocks of the U.S. America is Brontosaurus. The fact is that, if we wish to make an intelligent comparison of the sizes of different animals, we have carefully to ascertain not merely the length measurements, but the _proportions_ of the various parts, and the actual bulk and probable weight of the beasts under consideration. Also (and this is a very important and decisive matter) we must know whether the beasts were terrestrial in habit, walking with their bodies raised high on their legs, or whether they were aquatic and swam in the lakes or seas, their bodies buoyed up and supported by the water. By far the biggest animals of which we have any knowledge are the various kinds of whales still flourishing in the sea. A mechanical limit is set to the size of land-walking animals, and that limit has been reached by the elephant "Flesh and blood," and we may add "bone," cannot carry on dry land a greater bulk than his. He is always in danger of sinking by his own weight into soft earth and bog. His legs have to be much thicker in proportion than those of smaller animals–made of the same material–or they would bend and snap. His feet have to be padded with huge discs of fat and fibre to ease the local pressure, and his legs are kept straight not bent at the joints, when he stands (a fact to which Shakespeare makes Ulysses refer), so that the vast weight of his body shall be supported by the stiff column formed by the upper and lower half of the limb-bones kept upright in one straight line. A well-grown elephant weighs five tons. Compare his