626 Proceedings. 



Mr. Kirk agreed with Dr. Hector regarding the difficulty in understanding how such 

 plants as Magnolia and the tulip tree could not only exist but perfect their flowers and 

 fruit where light was absent for six months of the year. The absence also of all forms of 

 low plant-life, which might naturally be expected under such circumstances, required 

 explanation. 



Mr. Cox thought the author had overlooked the evidence of former glacial periods at 

 successive intervals as far back as the Devonian epoch, with intervening periods, during 

 which warmer conditions prevailed. 



Mr. Martin Chapman said that, unless the oldest formations were proved to be 

 sedimentary, the presence of water in them would prove nothing, as water must infiltrate 

 the deepest rock we can reach. He thought the temperature at which plant-life could 

 exist had been understated, from his having collected organisms in the hot springs in 

 Hecla (Iceland), which had a very high temperature. 



Mr. Carruthers thought that the paper was so important that its discussion should 

 have been deferred. He thought it not yet proved that there was a central heat, and 

 certainly not that it could influence climate. The argument derived from increase of 

 temperatui'e with depth in the earth's crust only proved a modified form of volcanic 

 action — in some places greater than in others. The greatest depths to which we reached 

 were the bottoms of the oceans, and there we found no evidence of a higher temperature, 

 but the reverse. In open oceans it might be argued that this was due to the removal of 

 the heat by currents ; but in the case of the Mediterranean, and also in Loch Ness, which 

 are deep holes without an outlet, excepting for the surface water, the temperature at the 

 bottom is the same as the average winter temperature of the air at the surface. In the 

 nebular theory heat had always been assumed as being the expanding force which was 

 gradually lost ; but this was not proved. Cosmical dust is not kept apart by heat, but by 

 the continuous motion of the particles. He thought the balance of evidence was against 

 the theory of central heat. If the earth had once been hotter it would have become 

 smaller in cooling, and its velocity of rotation would have increased ; but this was 

 contrary to fact, as the rotation had been retarded by about three hours since exact 

 observations were first made. With regard to what had been said about the thickness 

 of the earth's crust, the existence of tides proved that it must be so great as to be 

 absolutely rigid. He considered it quite possible for plants to live in darkness if they 

 remained dormant, like geraniums which are placed in a dark cellar during the winter. 



Mr. Travers, in reply, said he had not advanced any theory of his own, but merely 

 wished to direct attention to views that were gainmg ground. He thought that when 

 geologists had studied the works to which he had referred, they would very much alter 

 their present opinions on the subject. 



Owing to the late hour at which the discussion terminated, several papers were held 

 over for next meeting. 



FoUETH Meeting. Isi Sciitember, 1877. 

 W. T. L. Travers, M.H.E., F.L.S., President, in the chair. 

 Xew Members. — A. T. Maginnity, J. J. Clierrett. 



Attention was drawn to several additions to the libraiy, viz., publications on the 

 geological survey of the United States and other works received through the Smithsonian 



