For the information of the non-scientific, it may be necessary to mention that the ivory alluded to in the preceding tale, is derived from the tusks of the mammoth, or fossil elephant of the geologist. The remains of this gigantic quadruped are found all over the northern hemisphere, from the 40th to the 75th degree of latitude: but most abundantly in the region which lies between the mountains of Central Asia and the shores and islands of the Frozen Sea. So profusely do they exist in this region, that the tusks have for more than a century constituted an important article of traffic--furnishing a large proportion of the ivory required by the carver and turner. The remains lie imbedded in the upper tertiary clays and gravels; and these, by exposure to the river-currents, to the waves of the sea, and other erosive agencies, are frequently swept away during the thaws of summer, leaving tusks and bones in masses, and occasionally even entire skeletons, in a wonderful state of preservation. The most perfect specimen yet obtained, and from the study of which the zoologist has been enabled to arrive at an accurate knowledge of the structure and habits of the mammoth, is that discovered by a Tungusian fisherman, near the mouth of the river Lena, in the summer of 1799. Being in the habit of collecting tusks among the debris of the gravel-cliffs, (for it is generally at a considerable elevation in the cliffs and river banks that the remains occur,) he observed a strange shapeless mass projecting from an ice-bank some fifty or sixty feet above the river; during next summer's thaw he saw the same object, rather more disengaged from amongst the ice; in 1801 he could distinctly perceive the tusk and flank of an immense animal; and in 1803, in consequence of an earlier and more powerful thaw, the huge carcase became entirely disengaged, and fell on the sandbank beneath. In the spring of the following year the fisherman cut off the tusks, which he sold for fifty rubles (£7, 10s.;) and two years afterward, our countryman, Mr. Adams, visited the spot, and gives the following account of the extraordinary phenomenon: