SCIENTIFIC LITERATURE.
GEOLOGY.
In accordance with the general results of Mr. G. K. Gilbert’s investigation of recent earth movements in the Great Lakes region—that the whole district is being lifted on one side or depressed on the other, so that its plane is bodily canted toward the south-southwest, and that the rate of change is such that the two ends of a line one hundred miles long, running in a south-southwest direction, are relatively displaced four tenths of a foot in one hundred years—certain general consequences ensue. The waters of each lake are gradually rising on the southern and western shores, or falling on the northern and eastern shores, or both. This change is not directly obvious, because masked by temporary changes due to inequalities of rainfall and evaporation and various other causes, but it affects the mean height of the lake surface. In Lake Ontario the water is advancing on all shores, the rate at any place being proportional to its distance from the isobase through the outlet. At Hamilton and Port Dalhousie it amounts to six inches in a century. The water also advances on all shores of Lake Erie, most rapidly at Toledo and Sandusky, where the change is eight or nine inches a century. All about Lake Huron the water is falling, most rapidly at the north and northeast; at Mackinac the rate is six inches, and at the mouth of French River ten inches a century. On Lake Superior the isobase of the outlet cuts the shore at the international boundary; the water is advancing on the American shore, and sinking on the Canadian. At Duluth the advance is six inches, and at Huron Bay the recession is five inches a century. The shores of Lake Michigan are divided by the Port Huron isobase. North of Oconto and Manistee the water is falling; south of these places it is rising, the rate at Milwaukee being five or six inches a century, and at Chicago nine or ten inches. Eventually, unless a dam is erected to prevent it, Lake Michigan will again overflow to the Illinois River, its discharge occupying the channel carved by the outlet of a Pleistocene glacial lake. The summit in that channel is now about eight feet above the mean level of the lake, and the time before it will be overtopped may be computed. For the mean lake stage such discharge will begin in about one thousand years, and after fifteen hundred years there will be no interruption. In about two thousand years the Illinois River and the Niagara will carry equal portions of the surplus water of the Great Lakes. In twenty-five hundred years the discharge of the Niagara will be intermittent, failing at low stages of the lake, and in thirty-five hundred years there will be no Niagara. The basin of Lake Erie will then be tributary to Lake Huron, the current being reversed in the Detroit and St. Clair channels.
GEOGRAPHY.
Relating to the Royal Geographical Society the story of his exploration of the Bolivian Andes, Sir Martin Conway spoke of his journey by way of the Arequipa Railroad, Peru, to Lake Titicaca. That remarkable sheet of water is fourteen times the size of the Lake of Geneva and twelve thousand feet above the sea, and might be regarded as the remnant of a far greater inland sea, now shrunk away. Driving from Chililaya, he reached the snowy mountain called the Cordillera Real—the backbone of Bolivia—which he had come especially to visit, and in the region of which he spent four months. To the east the mountains fell very rapidly to a low hill country and the fertile valleys that send their waters to the river Beni. On the other side lay a high plateau, at a uniform altitude of from twelve thousand to thirteen thousand feet, from which the tops of low rocky hills here and there emerged. This plateau had obviously been at one time submerged; evidence was plentiful that in ancient times the glaciers enveloped a large part of the slopes that led down to it from the main Cordilleras and reached down many miles farther than now. In the immense pile of débris left by the glaciers deep valleys were afterward cut by the action of water, and into these valleys the glaciers of a second period of advance protruded their snouts, depositing moraines that could still be traced in situ as much as four or five miles below the present limit of the ice. Contrary to the apparently general impression that the peaks of the Cordilleras were volcanic, the author had not been able to find any trace of volcanic action along the axis of the range. The Cordillera Real had been elevated by a great earth movement, and the heart of the range consisted of granites, schists and similar rocks. The whole range might be described as highly mineralized. Gold was found at several points, but the chief auriferous valleys were those on the east side of the range. Just below the snowy mass of Cacaaca on the west was a really enormous vein of tin; and antimony, cobalt and platinum have been found in different parts. The great copper deposits were not in this range, but farther west. The flora of the high regions of the Cordillera Real was apparently sparse, but is probably more abundant in the rainy season. Bird life was more prolific and birds were numerous, at suitable places, up to an altitude of seventeen thousand feet above the sea.
ZOOLOGY.
The most recent elementary text-book in zoölogy is from the press of The Macmillan Co. Professor and Mrs. Charles B. Davenport are the joint authors. It is recognized now-a-days that what the general high school or elementary student in zoölogy needs is not professional training in that subject, but rather an opportunity to view the field so that he may have as wide an acquaintance as may be of the forms of animals and of their doings. This he needs that he may have an interest in the things of nature and that he may be a more intelligent member of society in the things pertaining to his welfare as affected by animals. The book is therefore an attempt to restore the old natural history in a newer garb. The text is divided into twenty-one chapters. The first of these deals with ‘The Grasshopper and its Allies,’ followed by others upon the butterfly, beetle, fly, spider, etc., similarly treated. Each chapter has one or two ‘keys’—that is, arrangements whereby the families of animals may be determined. The book is richly illustrated by means of half-tone and line reproduction; a number of photographs are from life, and one of these is a flash-light photograph of a slug and an earthworm crawling upon a pavement at night! Outlines for simple laboratory work and a list of books dealing with the classification and habits of American animals are to be found in an appendix. Many good things might be said of this contribution to zoölogical text-books. This ought to be said, that it will be a book which will be of value to any person who, while upon his holiday trip, wishes to learn about the animals he may come across.
ORNITHOLOGY.
Mr. Chapman is equally at home with camera or pen. In ‘Bird Studies with a Camera, with Introductory Chapters on the Outfit and Methods of the Bird Photographer,’ he gives us some of his many experiences from Central Park to the swamps of Florida and the bare rocks of the Gulf of St. Lawrence. The first two chapters are devoted to a brief discussion of the outfit and methods of the bird photographer, and these any one thinking of taking up this branch of art will do well to read carefully. Mr. Chapman considers that a 4×5 plate is the size best adapted for general purposes, and notes that while a lens with short focus may serve for photographing nests and eggs, for the birds themselves a rapid lens with focus of fourteen to eighteen inches should be used. The rest of the book is for the general reader, and contains many facts of interest concerning the haunts, habits, and home life of a number of birds from the well-known sparrow to the unfamiliar pelican, the accounts of the Bird Rock and Pelican Island being the most interesting. Some of the illustrations are a little disappointing, and emphasize the difficulties of photographing wild birds, but there is ample compensation for these in the excellence of others, particularly those devoted to Percé, Bonaventure and Bird Rock. This is equally true of birds and scenery, the views of Percé Rock being the finest that have fallen under our notice. Mr. Chapman’s estimate of the feathered population of Great Bird Rock, which he puts at 4,000, is by far the smallest yet made, and probably has the soundest basis, and shows a sad diminution from the hosts of fifty years ago.