Page:Popular Science Monthly Volume 1.djvu/521

Rh pounds each. This is just about one-half the estimated weight of the largest of the pyramids. To convey this amount by railway carriages, of 8 tons each capacity, would require 389,121 carriages, and, if of 20 feet length, they would make a train 1,473 miles long.

When we consider that for each year and upon each square mile of surface along our ocean border, and many miles inland, so vast a volume of water falls, we are astonished at the grandeur and vastness of some of the most common of the operations of Nature.

Prof. Agassiz's South-American Observations.—Prof. Agassiz and his scientific party are continuing their explorations of the South-American coast, in the steamer Hassler, and the professor has just made a second report to the Superintendent of the Coast Survey on the progress of his observations. As is well known, Prof. Agassiz undertook this expedition to accumulate evidence in regard to the extent of glacial action in producing geological effects. He has been a student of glaciers for forty years, grew up in a glacial region, and is familiar with the phenomena; early framed a theory upon the subject, and felt so certain of the truth of his views, that he predicted with great confidence the results of the explorations now undertaken. He says: "As soon as geologists have learned to appreciate the extent to which our globe has been covered and fashioned by ice, they may be less inclined to advocate changes of level between land and sea, wherever they meet with the evidence of the action of water, especially where no marine remains of any kind mark the presence of the sea." He confirms many of Darwin's observations made in the same region thirty years ago, but thinks he ascribed too much to the agency of upheavals. Nevertheless, he discovered a salt-pool with marine animals, in the interior, near Possession Bay, which were undoubtedly due to upheaval. He says:

About a mile from the shore bluff, I found, nearly 150 feet above the sea-level, a salt-pool, in which, to my great surprise, marine shells, identical with those now living along the shore, were abundant. They were in a perfect state of preservation, and many of them were alive; so that I gathered a number of specimens with the living animal, which I have preserved in alcohol. The most common were ferns, myrtilus, buccinum, fissurella, putella, voluta, etc., all found in apparently the same numeric relation as that in which they now exist in the sea below the cliff. The presence of this pool, with its living inhabitants, shows a very recent upheaval of the coast. The period at which it may have taken place it is hardly possible to determine without a more extensive survey.

But these and other evidences of upheaval do not disturb his profound conviction that ice has been the grand agency by which the southern continent has been moulded, as appears from the following:

It was not till we rounded Cape Froward [sic] that I felt confident that the range of hills immediately in sight along the channel we followed had assumed their present appearance in consequence of abrasion by ice. Now, however, that I have seen the whole length of the Straits of Magellan, have passed through Smyth's Channel, and visited Chile, I am prepared to maintain that the whole southern extremity of the American Continent has been uniformly moulded by a continuous sheet of ice. Everywhere we saw the rounded, undulating forms so well known to the students of glacial phenomena as roches moutonnées, combined with the polished surfaces scored by grooves and furrows, running in one and the same direction; while rocks of unequal hardness, dikes traversing other rocks, slates on edges, were all cut to one level. In short, the surface features of the Straits of Magellan have much the same aspect as the glaciated surfaces of the Northern Hemisphere. Whenever the furrows and scratches were well preserved, their trend was northern.

Notes on the Seychelles Islands.—In August, 1871, Nicholas Pike, Esq., U. S. consul at Mauritius, visited the Seychelles Islands, a group lying 900 miles northeast of Mauritius, in the Indian Ocean. They are 29 in number, some of them mountainous, comprising about 50,000 acres of land, and lie between 3° 33' and 5° 45' south latitude. Most of them are covered with tropical vegetation.

The shores are fringed with coral-reefs in all places favorable to their growth. Gigantic astræas, brain-corals, madrepores, and coral shrubbery of many hues, cover the reefs of which they form a part.

Consul Pike visited many of the islands and made an interesting sketch of their