Page:Quarterly Journal of the Geological Society of London, vol. 33.djvu/102

72 P. M. DUNCAN ON THE ECHINODEKMATA OF THE of the earth's surface to another would disturb the equilibrium, we must remember that this action would be mostly compensative; and if the cumulative effect of many such disturbances might be a partial readjustment of the mass, we must regard such movements only as a tendency to keep the whole mass and its axis of rotation as it was in spite of the transference of portions from one place to another by denudation. Moreover he disputed the data on which the views advocated by both the present and the late President were founded. He asked whether we should say that the climate of the period of our older river-gravels was that 'of Egypt or of Northern Siberia, seeing that the Corbicula jtuminalis and Unio littoralis were now found only much further south ; while the hairy elephant and rein- deer, which had once lived with them, were now held to prove an arctic climate. When we know that flowering plants and ever- greens now live in Alpine regions, where they are buried in total darkness under snow for four months, shall we say that the absence of light would render it impossible for evergreens and flowers to have flourished where the arctic winter-night is four months long, even though we could account for a milder climate by geographical changes ? Mr. Woodwakd remarked that as it was not merely a question of one fauna and flora, Mr. Hughes's statements must be received with caution. There were evidences in northern latitudes, not only of a Miocene, but also a Carboniferous, a Jurassic, and Cretaceous flora. Nor was it a question merely of lowly organized plants which would be more likely to withstand the climate ; for Prof. Nordenskiold had found tree-trunks standing erect in the soil in which they grew ; and it was impossible for them to have grown in a climate so rigorous as now exists at that latitude. If the geologists are wrong in the con- clusions they have drawn from these facts, let the astronomers show them how to account for the occurrence of fossils indicative of such a warm climate in such high northern latitudes ; for the absence of cold must be accounted for to explain the growth of these trees in that spot. Prof. Ansted maintained that the geologists had certain natural- history facts on their side with regard to the occurrence of fossils near the poles ; it remained, therefore, for the astronomers and physicists to find a new theory to account for these facts. Prof. Green thought that the astronomers should be asked if the change of axis was a possible explanation, and to calculate what would be the result of a change in the distribution of land and sea, and how such a change would affect the position of the poles. The question was one of mechanics. Mr. Sorby considered that the amount of heat and light received from the sun should also be taken into account, and the fact that this may have varied at different periods. Sir Antonio Beady stated that there were many facts which tended to prove that the sun had varied in heat &c. But the sun had probably little to do with the warmer climate of the poles in past ages. The heat of the earth in its various stages of cooling