New Method of Calculating the Duration of Geological Periods

THR Rev. Prof. S. Haughton read a paper, in which he said the problem had two sides—in the first place, it was a mathematical problem possessing very great interest from its own intrinsic elements; and, secondly, from the way in which he had used it, it was capable of throwing light on the method of setting a limit to the duration of geological periods, which, as they all knew, was one of the most interesting questions of recent times. They owed a debt of gratitude to Sir William Thomson for having directed attention to this most important question. He (Sir Wiiliam) had ventured to put a curb into the mouths of the geologists, and made them talk' less'wildly than they used; and he was sure that Sir William and others, b°th geologists and physicists, would agree with him that any new method of throwing light on this question was deserving of consideration. He had ventured to connect with this paper one on the solar eclipse of Agathocles, because it had a direct bearing on the coefficient of tidal retardation of which he made use in the present. Professor Haughton's method of ascertaining the limit of geological periods is based on the disturbances which have taken place of the axis of the earth's figure. There was no continent whose geological period was more distinctly marked than that of Asia and Europe—viz. , by the nummu- litic limestone. and he therefore selected that to illustrate his theory. Omitting the details of the process, the conclusion to which he arrived was that such a disturbance of the axis of figure as was produced by the “ manufacture” of Asia and Europe would give a period of 640,000 years, or within a million of years, allowing for errors of coefficients and corrections of data. Of course that would be a million of years plus x, an unknown quantity—the age of the nummulitic limestone, which geologists might say was a very large quantity. The discussion was opened by Sir William Thomson, who said he had no doubt the professor's figures represented, within very wide limits, the time that would be taken to reduce the disturbance to a point at which it would be imperceptible to astronomers. But if not absolutely expressing dissent, he must put in a moderate protest against allowing too much weight to his inferences. It was a question to what degree the change at the upheaval of the nummulitic limestone was sudden. If sudden, say within a year, the effect no doubt would closely correspond to Professor litic limestone, the utmost it would do would be to measure the time between the elevation of beds already formed in the bottom of the sea and the present day. Another difficulty was that, although there might be elevation of this kind disturbing the equilibrium in one direction, there might be others succeeding in the same or other directions which would either neutralize or increase their effects. Sir William Thomson referred to evidences of glacial action in India. Astronomers, he said, were willing to allow any amount of change in the earth's axis if the geologists would find the requisite change in the distribution of the solid matter of the earth to account for it. Professor Haughton, in replying, reminded them that his problem was one of pure mathematics. He had supposed that a continent suddenly raised from below the ocean would produce such and such a result. He did not suppose that Nature acted in that way, but that she acted in a way equivalent to it. So that if the change took place bit by bit, he had only to express the result in a different form, and to say that the continent of Europe and Asia took about 600,000 years to form. He felt that there were serious objections to the cut and dried explanation of change ORNAMENTAL ARM-CHAIR, BY O. SCHUH, UPHOLSTERER, VIENNA.—From the Workshop. Haughton's figures. But to what extent the earth's axis would vary in consequence of gradual changes in the solid matter of which the earth was composed was a question susceptible of being very incompletely answered. He felt exceedingly glad that the subject had been brought forward, for the professor had certainly given them a true ground for estimating geological dates. Great changes in the earth's solid mass have been proved, but it was a question for geologists whether any change had taken place within the compass of a year, of sufficient magnitude to materially alter the earth's surface. There could be no doubt that there had been no such sudden change during the past thousand years. Mr. Evans thought that there would be great difficulty in estimating geological periods from the variations between the axis of figure and the axis of rotation, inasmuch as at no given time could they have been any great distance apart. If that were so this suggestive methodof measuring geological time lost much of its value. With regard to the nummu of climates by moving the pole. The lias fossils formed a complete ring around the pole. He was afraid, therefore, that they must be content to refer the almost tropical climate of which these fossils spoke to the former hotter condition of the earth.

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