xlviii PROCEEDIlfGfS OF THE GEOLOGICAL SOCIETr. 



peratures and currents, with instruments prepared for the occasion, 

 I naust refer to the papers by Dr. Carpenter and his colleagues (to 

 whom I am much indebted for the perusal of the last Report, now 

 going through the press), in the ' Proceedings of the liojal So- 

 ciety'*, for the varied information respecting the composition 

 of sea-water at different depths, the gases contained in it, and the 

 speculations on oceanic currents. The points that more particularly 

 interest us are those bearing on geological investigations. 



In first drawing the attention of the Eoyal Society to the im- 

 portance of undertaking deep oceanic researches, Prof. Wyville 

 Thomson referred to the recent discovery by Prof. Sars of a small cri- 

 noid belonging to an order supposed to be extinct, and which flourished 

 from Jurassic to Cretaceous times ; he suggested the probability of 

 the continuity of the ancient chalk-sea with the present abyssal 

 depths of the Atlantic, as such depths would be but little affected by 

 any of the later oscillations of the earth's crust in the northern hemi- 

 sphere, as, since the commencement of the Tertiary epoch, they pro- 

 bably had not much exceeded 1000 ft. The result of the first expe- 

 dition was more than sufficient to confirm the most sanguine antici- 

 pations. Dr. Carpenter, on its return, reported that, of the higher 

 types of marine animals which they had discovered, " many carry us 

 back in a remarkable manner to the Cretaceous epoch;" and, again, 

 it " seems on general grounds highly probable that the deposit of Olo- 

 bigerina-mud has been going on from the Cretaceous epoch to the 

 present time (as there is much reason to suppose that it did elsewhere 

 in anterior geological periods), this mud not being merely a chalk 

 formation, but a continuation of the chalk formation." These views 

 have a high significance and interest. Let us see how far we can 

 adopt them. 



The Atlantic abyssal mud has been found to contain from 50 

 to 60 per cent, of carbonate of lime, 20 to 30 of silica, with small 

 variable proportions of alumina, magnesia, and oxide of iron. Its 

 appearance, when dry, is chalk-like ; but it is to be observed that our 

 white chalk is a much more homogeneous rock, containing from 

 95 to 99 per cent, of carbonate of lime, while even our grey chalk 

 contains from 80 to 90 per cent f. The larger proportion of cal- 



* Proc. Eoy. Soc. vol. xvii. pp. 168-200; vol. xviii. pp. 397-492; and 

 vol. xix. pp. 146-222. 



t Since writing the above, Mr. David Forbes has kindly obliged me with the 

 following observations: — "The specimens of Atlantic mud or soundings which 

 I have examined, differ very essentially from chalk in composition ; and no 

 single one of them (if consolidated) could be entitled to the appellation of 



