548 report — 1878. 



3. Concerning the Extent of Geological Time. By Rev. M. H. Close, F.G.S. 



This paper was only intended to afford desired opportunity for viva voce discus- 

 sion on the above subject. Since geology has her own strong and unrefuted 

 arguments for the great extent of geological time, it is not logically necessary for 

 her to do more than to show, if it can be shown, that the physical arguments for 

 the very inconvenient restriction thereof rest upon still unproved assumptions. 

 The argument from the rate of cooling of the earth seems to have been satis- 

 factorily shown by Mr. T. Mellard Reade to be quite inconclusive. The argument 

 from the probable duration of the sun's radiation of heat assumes, inter alia, that 

 the original nebula from which the solar system was formed was cold, and -also 

 that the unit of gravitation, relatively to the mass of that system, has been constant 

 from the time when that mass began to fall together, and throughout the enormous 

 interstellar distance which has doubtless been traversed by it since that time. Dr. 

 Croll's suggestion in answer to the former of these assumptions is logically suffi- 

 cient as a reply to the whole of this argument. Nevertheless, it may be added, as 

 to the latter assumption, that those physicists who have entered upon certain 

 speculations as to the cause of gravitation cannot deny that it is perfectly credible, 

 and even probable, that gravitation is not an essential accompaniment of matter, 

 and that the unit of gravitation may not be constant throughout all time and 

 space. The argument from the earth's figure in connection with the retardation of 

 her rotation by the ocean tides depends upon the doctrine of the steel-rigidity of 

 the earth taken as a whole, as do also the calculations of various writers on 

 subjects which bear, in different ways, on the present one. However, Sir "W. 

 Thomson himself has greatly weakened the support of this doctrine. But geology 

 (as regards the matter in hand) is not concerned to question it ; although it is, at 

 first sight, a difficulty. The results obtained by the Tide Committee of the Asso- 

 ciation point to the conclusion that there is an 18'6 year-tide in the body of the 

 earth depending upon the revolution of the moon's nodes, and that the rigidity of 

 the earth, even if it be, in one sense, as high as that of steel, is yet a viscous 

 rigidity, by which she may yield almost indefinitely to sufficient long-continued 

 straining forces. Other considerations confirm this latter position. This 18 - G 

 year-tide, whether resulting from such viscosity proper, or from plasticity of a 

 different kind, must cause a variation in the earth's rate of rotation having the 

 same period. This variation would probably be sensible if looked for by the 

 astronomers, who would confer a boon on the geologists by endeavouring to detect 

 it. Dr. John Evans's suggestion of the possibly considerable mobility of the axis 

 of rotation relatively to the body of the earth bears in certain ways on the 

 present question ; the mechanical objection to it, already greatly weakened by 

 Rev. 0. Fisher, might be quite removed by the investigation suggested.* 



4. On the Earth's Axis. By Rev. Professor Haughton, M.B., F.R.S. 



5. Geological Results of the late British Arctic Expedition-. 

 By Captain Feildem, B.A., and Mr. De Rance. 



The author describes Laurentian gneiss of Cape Sabine, and the Cape Rawson 

 beds of Grinnell Land; the overlying Silurian rocks; the Devonian rocks of Dana 

 Bay ; the Carboniferous Limestone of Feilden Peninsula, and the Miocene beds of 

 Lady Franklin Bay; the Pleistocene deposits and glaciation of the coasts of 

 Grinnell; and the method of formation of the Icefoot. 



He discusses the bearing of these results on what was already known on Arctic 

 geology.f 



* See ' Geological Magazine,' Oct. 1878. 



f See ' Quart. Jour. Geol. Soc' vol. xxxiv. p. 556. 



