Page:Popular Science Monthly Volume 52.djvu/248

234 geological relation. The oxide and carbonate are associated with dolomitic limestones of the lower Devonian, and may be traced into them by a gradual transition, as at the mines of Bakal, where the ore is hematite for some distance below the surface, then passes to spathic iron, and this into dolomitic limestone at a considerable depth.

After traversing the Urals to Zlatoust, where are the great iron and steel works that produce some of the finest weapons used in the Russian army, and that sent an elegant exhibit to the Chicago World's Fair, the excursion traversed the famous mining and mineral region of the Ilmen Mountains northward to Tagilsk and Ekaterinbourg. This portion of the route is treated of in several papers as follows: The Eastern Slope of the Urals (No. 5), by Prof. A. Karpinsky; The Minerals of Kussa and Miass (No. 4), by A. Arzruni; The Gold Deposits of the Southern Urals (No. 6), by N. Wyssotsky; The City of Ekaterinbourg and its Environs, especially in Reference to Prehistoric Archæology (No. 7), by Dr. O. Clerc; The Mining Districts of Tagil and Gora-Blagodat (No. 9), by Professor Tschernitschew; and one or two minor articles.

Professor Karpinsky gives an admirable account of the region of the eastern Urals and beyond, emphasizing the contrast between the two sides of the system. While the western slope passes by gradual and gentle undulations into the plains and steppes of European Russia, the Asiatic side has been enormously eroded away. A wide belt of country along the eastern base of the Urals, consisting of upturned and folded rocks identical with those of the mountains, has been leveled down to an absolute plain. Over this are spread the deposits of the Tertiary sea that reached in Pliocene time nearly to the central ranges of the Urals, and that has largely obliterated their eastern portion. These deposits stretch far away into the great Siberian plain. Along their western edge, and for some distance eastward, they are strewn with lakes—some fresh and some salt; some deep and narrow among the folds of the edge of the mountain region; others broad, shallow, and with flats and benches of gradual contraction in the level country to the east. Two striking views of this lake-bestrewn plain from the top of some of the Ilmen peaks are given in the monograph.

The gold of the Urals, of course, receives much attention in these papers; the placers are carefully described, and the quartz mining also, which in some districts is overtaking and surpassing the placers in output. Closely connected with these are the platinum workings, thus far wholly surface deposits. But it is of great scientific interest to note the definite tracing of this metal to its original rock source, associated with chromic iron in serpentines, which