348 P. M. DUNCAN ON SOME FOSSIL KEEF -BUILDING COKALS 



perate zone. Oblique as would be the path of many solar rays, still 

 the corresponding loss of temperature would be compensated for by 

 the warming of the atmosphere by the radiation from the masses 

 of the land-surfaces to the north and south. It is, moreover, reason- 

 able, according to the principles of thermodynamics, to assert that 

 the sun was then producing more heat, and that the internal tem- 

 perature of the globe was greater than now ; and this may have had 

 some slight influence. 



In bringing these theories before you, which have been in the 

 minds of so many geologists, and which have been brought forward 

 by succeeding generations of us, Belt and Woodward being their 

 last supporters, my excuse must be that possibly they may be im- 

 proved upon by those physicists who will admit the necessity of 

 comprehending biology in their dynamical and kinetic arguments, 

 — or that in the true interests of science they may be disproved, so 

 that we may seek explanations of the facts brought forward in this 

 and other cognate essays in other directions. 



Note. — This communication was forwarded to the Society before 

 my predecessor in the Presidential office read his admirable Address. 

 I now refer the reader to his remarks on those questions of astro- 

 nomical interest which I have introduced in this paper. (See 

 Anniversary Address of the President, John Evans, Esq., F.Ii.S., 

 Quart. Journ. Geol. Soc. vol. xxxii. Proe. p. 101 et seq.) 



EXPLANATION OF PLATE XXII. 



Fig. 1. Corallum of Heliastrcea tasmaniensis, sp. iioa'. 



2. Calice, magnified 3 diameters. 



3. Costse and exotheca, X 3. 



4. Calices of Thamnastrcea sera, sp. nov. 



5. Longitudinal section of corallum. 



6. Details of septa, X 3. 



Discussion *. 



Mr. Evans was glad to find that this subject, concerning which he 

 had lately expressed his own views, had been taken up by the 

 author; but he thought it possible that Dr. Duncan would, on 

 further consideration, be inclined to modify somewhat the theory 

 promulgated in this paper in favour of some other view. In order 

 to account for the occurrence of reef-building corals of Miocene 

 age in latitudes now too cold for them, the author had reverted to 

 the old^idea of the vertical position of the poles. If the interior of 

 the earth is fluid, a sliding crust such as the speaker had formerly 

 suggested is possible, though it would be difficult to prove the ex- 

 istence of a fluid interior, and still more difficult, did that exist, to 

 prove that the crust would slide on it. But even supposing the 

 earth to be a nearly solid body, elevations and depressions enough 



* This discussion relates also to Prof. Duncan's paper " On the Ecbinoder- 

 mata of the Australian Cainozoic Deposits." 



