Popular Science Monthly/Volume 57/August 1900/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 abvious, 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 textbook 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 zoælogical 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 4x5 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.
'Bird Homes,' by A. Radclyffe Dugmore, seems well adapted for its stated purpose of stimulating the love of birds, helping the ordinary unscientific person to get some closer glimpses of them, and aiding in the study of their wonderfully adapted nests and beautiful eggs. Furthermore, it will probably create a strong desire in the reader to become a photographer of birds and their nests. To further these aims we have a first part containing half-a-dozen chapters devoted among other things to birds' nests and eggs, photographing nests and young birds and the approximate dates when birds begin to nest, this being adapted to the vicinity of New York.
Following this is the bulk of the volume, containing brief descriptions of the birds, their nests, nesting places and eggs, and here the author has confessedly borrowed from Bendire, Davie and other well-known authorities, although one might wish that Mr. Dugmore had introduced more of his own observations, since those given incidentally in the first part are very interesting; where he indulges in theory he is less successful. In place of the usual method of studying the nest from the bird, we have that of studying the bird from the nest, and for this purpose the nests are grouped in classes, a chapter being devoted to each class; thus we have nests open, on the ground in open fields, marshes and generally open country; open nests in trees: nests in bridges, buildings, walls, etc. By this plan any one finding a nest can, with a little care and observation, identify the bird that made it. The illustrations, largely of nests and eggs, are a noteworthy feature of the book, although the three-color process which succeeded so admirably in Dr. Holland's Butterfly Book, is here as equally distinct a failure, the least bad of the colored plates being that showing the nest of the yellow-breasted chat, the worst that of the nest of the Baltimore oriole. Those in black and white, however, merit the highest praise, and this includes the smaller cuts introduced as decorative features in the first portion of the book. It would seem difficult in a half-tone to improve on the plate of young crested flycatchers for clearness of detail, while among others that deserve special mention for artistic effect is the wood thrush on nest, and the nests of the chestnut-sided, yellow, blue-winged and worm-eating warblers. The general 'get-up' of the book is excellent, and the printing of the plates separately permits the use of a dead-faced paper for the text, which is pleasant to the eye.