Page:Transactions NZ Institute Volume 10.djvu/35

Rh There has been no ice work going on there since the Colorado began to cut its mighty drain a mile and a quarter deep, where it is at the same time but one hundred and eighty feet across; the three hundred feet of the lowest portion of this extraordinary chasm being eroded through hard granite. When this great work commenced, according to reasonable calculations, the northern currents must have been spreading drift on the submerged eastern plains, if that operation went on during the glacial period of Sir Charles Lyell.

The moraines of ancient local glaciers may be seen on the slopes of these mountains below 39° N. latitude, and also upon those of the Sierra Nevada, still nearer to the tropics, but traces of general glaciation there or of northern drift on the shores of California of the same age as that on the eastern side of the Missouri have not hitherto been observed. The vast accumulations of shingle on the terraces of Oregon and Washington territory are as ancient, according to American geologists, as those of the highest plateau of the prairies east of the Rocky Mountains, and are composed, as the latter are likewise, of materials of local derivation. They were deposited there when the Cascade Range already presented a formidable wall, and previous to the time when Mount Hood, Mount Rainier, and Shasta, those grand "Lookers-on" of the Pacific Coast, were piled up.

The boulders which lie on these old shingle terraces on the sides of the Willamette and other valleys, and on the shores of Vancouver, may be pointed to as memorials of the "Great Age of Ice," but they cannot be proved to have travelled very far. The grey syenite of which the majority of them consist, is a distinguishing rock of the Cascade Range, from whence glaciers brought them down probably during a local period of cold.

On the Atlantic side of the Mississippi basin, erratics were dropped in certain meridians, as far south as the 37th degree of latitude, when the way was open over the great lake region then submerged to the polar sea, just as they are being now on the American side of the Atlantic, nearer to the tropic than they were at that era.

Ice-polished and striated boulders, floated from afar in distant ages, may lie buried under the soil of the Californian plains, but none have been discovered by American observers. I could see no foreign stones or ancient ice-marks on the slopes of Calaveras or Mariposa, above Yosemite.

There is a vast river in the Pacific coming from equatorial regions, entitled to be described in the same expressive language with which Maury introduces his readers to the consideration of the Gulf Stream. It sweeps near the coast of Japan past Yokohama, leaving the shores of Yesso further off than it does those of Nipon, and has flowed in the same course, tempering its climate and causing hurricanes in its seas, we may conclude from