Boyal Society of Edinburgh. 



311 



been, as I understand, withdrawn ; the bones of elephant and other 

 animals, bearing marks of human hands, are not yet accepted by 

 these naturalists. As to the Abbeville jaw-bone of a man, whose 

 jaw must have ceased chewing long before the flood, there is but 

 one opinion in England, which I am informed by Mr Evans is also 

 gaining ground in France — that the whole thing was an impudent 

 imposition. Mr Prestwich, who was once a believer, published his 

 recantation in the last Quarterly Journal of the Geological Society. 



It may be permitted me, perhaps, as one of the public, to offer 

 one more advice to the naturalist. He must take care not only 

 that his reasoning is logical, his inferences cautious and careful, 

 but he will do well to avoid even the appearance of disputing for 

 victory. Science has no enemies if its votaries do not raise them 

 up by indiscretion and intemperance. 



Monday, 21st December 1863.— Dr CHEISTISON, V.P., 

 in the Chair. 



The following Communications were read : — 



1. On the Morphological Eelationships of the Molluscoida 

 and Coelenterata and of their leading members, inter se. 

 Bj John Denis Macdonald, E.N., F.E.S., Surgeon of 

 H.M.S. "Icarus." Communicated by Professor Maclagan. 



2. On the External Anatomy of a New Mediterranean 

 Pteropod. By John Denis Macdonald, E.N. Communi- 

 cated by Professor Maclagan. 



3. On the Limits of our Knowledge respecting the Theory of 



Parallels. By Professor Kelland. 



The Author has in this paper traced to its consequences the 

 assumption, as if it were an axiom, of the proposition " That the 

 angles of a triangle are together less than two right angles." The 

 results as regards the theory of parallels are such as to imply that 

 such lines would have most of the properties of equal circles ex- 

 terior to one another. 



Professor Tait reminded the Society that, at the close of last 

 session, he and Balfour Stewart, E.E.S., of the Kew Observatory, had 

 deposited with the Secretary a sealed packet containing the coin- 

 cident results of certain investigations which they had separately 

 carried on from totally distinct points of view, and which appeared 

 to lead to a new principle in Natural Philosophy. 



Experimental attempts at verifications of this principle have 

 since been made by them in various ways, and others are in pro- 

 gress. Meanwhile, the authors desire to put on record that it 

 appears probable, from their experiments, that the viscosity, &c., of 



