458	GEOLOGY AND MINERAL RESOURCES.
the Bay of Katmai, on the south coast of Aliaska, Wossnessensky obtained Jurassic ammonites and fragments of belemnites. It is possible that the sulphuret of copper, reported from the north shore of Aliaska, may be contained in rocks of similar age. This completes the list of known localities of rocks older than the Cretaceous in Alaska.
Early in the Cretaceous period the Cascade Ranges and their analogues to the north were washed by the waves of the great Cretaceous sea. Later in the same epoch the Coast Ranges were uplifted by plutonic force. To the immense convulsions which elevated the great volcanic peaks of these ranges is probably due that immense system of canals, islands, fiords, and inlets which are so conspicuous on the northwest coast. Most of the Aleutian Islands are probably of later elevation.
Some portions of the sea-bed, having been simultaneously elevated, became covered with dense forests. From these the important beds of Cretaceous lignites on the west coast were formed. Gradual elevation of the coast continued. In the early Miocene (Eocene ? of Foster, Mississippi Valley, p. 322) the climate of Greenland, Spitzbergen, the Arctic Islands, the north-ern part of America and Europe, was genial and temperate. Immense forests of trees, now confined to far more southern latitudes, existed all over the north. In the valley of the Yukon sycamores (Platanus) were abundant. On the shores of Cook's Inlet, pines (Pinus), redwoods (Sequoia), elms (Ulmus), four species of oaks (Quercus), three of walnuts (7uglans), ilex, maple, liquidambar, taxodium, and many other trees of the temperate zone, beside Myrica and Spircea, grew in profusion. From this locality fifty-two species of fossil plants are described, of which twenty-two are common to beds of the same age in Northern Europe, and a smaller number to Northern Asia, Greenland, Spitzbergen, Vancouver Island, and Oregon. Species of Sequoia, Corylus, and Pecopteris, have been obtained from Kake Strait. The debris of these forests forms the great lignite beds of Fort Union, Nebraska, as well as most of the beds of northern lignite. A depression of this part of the continent then began ; the sea covered the site of the sycamore groves of the Yukon, and in the' highest rocks (the brown sandstones of Nulato) of that valley we find the re-mains of Ostrea and other marine shell-fish. The last and still