Ascending to the gallery above, we find a large and varied collection of implements of savage tribes and relics of prehistoric man. A huge case of skulls, whose owners lived and breathed thousands of years ago, is a ghastly reminder of the continuity of human history. Implements of stone and flint from France, from Denmark, and from the Mississippi valley are silent witnesses of the days before the discovery of the art of working iron. There are also a couple of notable groups—one of opossums and one of muskrats. The latter is a singularly faithful reproduction of nature. It shows a muskrat swimming by the bank of a pond, whose glassy surface is blurred by the ripples that mark his course. White and yellow lilies float on the water, from which rises a muskrat house, opened at the side to show one of its inmates lunching upon a reed stem. The sandy bank of the pond is pierced by galleries from which there peeps a young rat. From the ceiling, in the center of the hall, there hangs a huge Indian war canoe, which once bore the warriors of the Bella Bella tribe, in British Columbia, over the waters of Queen Charlotte’s Sound. Though capacious enough to carry a small regiment, it was made from the wood of a single tree. [Illustration: THE MASTODON—AN EXTINCT INHABITANT OF NORTH AMERICA.] The third floor of the museum is devoted to collections of shells and minerals, which include a wealth of interesting specimens. There is a sheet of itacolumite, or flexible sandstone, from North Carolina, so arranged that its power of bending can be tested by turning a screw; there are stibnite (antimony ore) from Japan, galenite (lead ore) from Missouri, gold quartz from California, calamine from New Jersey, as well as chalcopyrite, marcasite, and a host of other minerals of strange name and form. On one small tray are grouped reproductions of the world’s most famous diamonds, showing the exact size and appearance of these little pebbles for which dynasties have been overthrown. One of them is labeled “the Koh-i-noor, value $1,000,000.” It is safe to say that Queen Victoria is not offering the original for sale at that price. And if the Koh-i-noor, which weighs 125 karats, is worth a million, what must be the value of the Great Mogul diamond, of 297 karats? Further down the same row of cases are amethysts, beryls, agates, and other semi-precious stones. Among these is a curious section of an agatized tree from Chalcedony Park, Arizona. It was mineralized by the waters of a hot silicated spring, the silica replacing the wood as it decayed, particle by particle.