552 J. F. Walker — Terebratula Morieri in England. 



could not slide over it, I grant that there would be truth in the 

 objection. But if the crust be considered flexible, as practically it 

 must be if of small thickness and liable to corrugation, then I do not 

 see why the rotation of the fluid should have the effect of pi-eventiug 

 the crust slipping over the nucleus, and adapting itself to such a 

 position of equilibrium, as any irregularities of thickness resulting 

 from corrugation might render necessary under the action of the 

 centrifugal force and gravitation. 



The final query put by Mr. Hill is this — "Will a change in 

 latitudes give the best explanation of the phenomena ? " To this I 

 reply, that we have four chief classes of facts to account for : 



1. The almost ubiquitous presence, either in present or past times, 

 of volcanic action ; apparently showing that wherever the earth's 

 surface is pierced to a sufScient depth, a molten stratum is tapped. 



2. The capacity for slipping towards certain lines which the crust 

 possesses, as proved by the lateral compression of the strata 

 along the flanks of mountain chains. 



3. The amount of horizontal compression of the superficial strata 

 being greater than the cooling of a solid earth can account for. 



4. Changes of climate — notably the existence of a warm climate 

 in former times near the North Pole. 



These are the phenomena, and it appears to me that these four 

 classes of facts point convergently towards the doctrine of a fluid 

 substratum. It is quite true that the question which I put to physicists 

 and now repeat was ivhetJier a fluid substratum over a rigid nucleus 

 loould not he compatible with mechanical considerations, and whether 

 under those circumstances changes in latitude would not residt from un- 

 equal thicTcening of the crust ? And I suggested that the present 

 distribution of the continents gives support to that idea. But I 

 was not seeking primarily to account for changes of climate in that 

 manner. That theory belongs to Dr. Evans ; and he has ably 

 defended it against Dr. Haughton's somewhat formidable objections 

 in his recent address to the British Association at Dublin, The sup- 

 position alternative to Dr. Evans', by which Dr. Haughton would 

 account for a former warm climate at the Pole through residual heat 

 in the earth, has, I think, been disposed of by anticipation in Sir W. 

 Thomson's paper on the Secular Cooling. 



V. — On the Occurrence oe Terebratula Morieri in England. 

 By John Francis Walker, M.A., F.G.S., etc. 



A VALUABLE paper by T. Davidson, Esq., F.E.S., appeared in 

 the Proceedings of the Dorset Natural History and Antiquarian 

 Field Club for 1877, " On the species of Brachiopoda that occur in 

 the Inferior Oolite at Bradford Abbas and its vicinity." Since then, 

 during a recent visit to this locality, I have added a few species to 

 this list, including two which have not been discovered in England 

 before. I propose to give a short account of these species, and also 

 a table showing the relative distribution of the Brachiopoda in the 

 Inferior Oolite and Fuller's Earth deposits at Cheltenham and 

 France, compared with this district. 



