Page:Popular Science Monthly Volume 50.djvu/878

856 head of this river, by Monctin twenty miles from the bay head, the bore is seen to best advantage; it rushes in ‘as a foaming breaker, five or six feet high, with a velocity of five or six miles an hour.’ The spring and neap tides have forty-five and thirty-eight feet range. The ebb tide runs like a mill race; the water rapidly sinking, and the river is reduced to a small meandering stream. It so remains about two hours, when the rushing waters of the bore are heard again, and the river is soon filled with their sweeping flood."

Necessities of Geological Time.—One of the questions considered by Prof. E. B. Poulton, in his presidential address before the Geological Section of the British Association, related to the length of time required for the development of animal life on the earth to its present condition—"whether the present state of paleontological and zoölogical knowledge increases or diminishes the weight of the opinion of Darwin, Huxley, and Spencer, that the time during which the geologists concluded that the fossiliferous rocks had been formed was utterly insufficient for organic evolution." The arguments of the physicists, derived from the supposed effect of tidal action upon the length of the day, and from the estimated length of the time occupied by the earth in cooling from an assumed temperature to its present condition, are shown to have been proved invalid as bases for calculating the probable age of the earth as a life-bearing body. The argument derived from the supposed life of the sun has not yet been ruled out, and that gives a maximum of five hundred million years. The computation of the time required for depositing the geological strata gives a minimum of seventy-three million and a maximum of six hundred and eighty million years—possibly four hundred million years. The author's inquiry as to how much of the whole scheme of organic evolution has been worked out in the time during which the fossiliferous rocks were formed does not deal with the time required for the origin of life or for the development of the lowest beings with which we are acquainted from the first formed beings, of which we know nothing; but only with so much of the process of evolution as we can infer from the structure of living and fossil forms. The comparison is made from a study of the evolution of the phyla. All available evidence points to the extreme slowness of progressive evolutionary changes in the cœlenterate phyla, although the protozoa are even more conservative. When we consider further on the five cœlenterate phyla that occur fossil, we shall find that the progressive changes were slower, and indeed hardly appreciable in the echinoderms and gephyrea, as compared with the mollusca, appendiculata, and vertebrata. Within these latter phyla we have evidence for the evolution of higher groups, presenting a more or less marked advance in organization. As a whole, the comparison is quite enough to necessitate a very large increase in the time estimated by the geologist. We can hardly escape the conclusion that, for the development of the arthropod branches from a common chetopodlike ancestor and for the further development of the classes of each branch, a period many times the length of the fossiliferous series is required. The evolution of the ancestor of each of the higher animal phyla probably occupied as long a period as that required for the evolution which subsequently occurred within the phylum. But the consideration of the higher phyla which occur fossil, except the vertebrata, leads to the irresistible conclusion that the whole period in which the fossiliferous rocks were laid down must be multiplied several times for this later history alone. The period thus obtained requires to be again increased and perhaps doubled for the earlier history.

The New Zealand Alps.—The "Alps" of the Southern Island of New Zealand are described by Mr. Fitz-Gerald as being more like the Pyrenees than the Swiss Alps in structure, in that they are a single range rather than constituted of parallel folds. The highest peak, Aorangi, or Mount Cook, is 12,349 feet high, but not many of the others rise above 10,000 feet. The snow line is, however, 2,000 feet lower than in Switzerland, and the glaciers descend much nearer to the sea level, the great Tasman Glacier coming down to about 2,350 feet, several to 1,200 feet, and the Fox Glacier to 700 feat. Nearly twice as much snow falls upon some of their slopes as at corresponding positions on the