As for the size of the mastodon, this, like that of the mammoth, is popularly much over-estimated, and it is more than doubtful if any attained the height of a full-grown African elephant. The largest femur, or thigh-bone, that has come under the writer's notice was one he measured as it lay in the earth at Kimmswick, and this was just four feet long, three inches shorter than the thigh-bone of Jumbo. Several of the largest thigh-bones measured show so striking an unanimity in size, between 46 and 47 inches in length, that we may be pretty sure they represent the average old "bull" mastodon, and if we say that these animals stood ten feet high we are probably doing them full justice. An occasional tusk reaches a length of ten feet, but seven or eight is the usual size, with a diameter of as many inches, and this is no larger than the tusks of the African elephant would grow if they had a chance. It is painful to be obliged to scale down the mastodon as we have just done the mammoth, but if any reader knows of specimens larger than those noted, he should by all means publish their measurements.[20] [20] _As skeletons are sometimes mounted, they stand a full foot or more higher at the shoulders than the animal stood in life, this being caused by raising the body until the shoulder-blades are far below the tips of the vertebrae, a position they never assume in life._ The disappearance of the mastodon is as difficult to account for as that of the mammoth, and, as will be noted, there is absolutely no evidence to show that man had any hand in it. Neither can it be ascribed to change of climate, for the mastodon, as indicated by the wide distribution of its bones, was apparently adapted to a great diversity of climates, and was as much at home amid the cool swamps of Michigan and New York as on the warm savannas of Florida and Louisiana. Certainly the much used, and abused, glacial epoch cannot be held accountable for the extermination of the creature, for the mastodon came into New York after the recession of the great ice-sheet, and tarried to so late a date that bones buried in the swamps retain much of their animal matter. So recent, comparatively speaking, has been the disappearance of the mastodon, and so fresh-looking are some of its bones, that Thomas Jefferson thought in his day that it might still be living in some part of the then unexplored Northwest.