246 TRE ATLANTIC. [chap. v. 



CHAPTER Y. 



GENERAL CONCLUSIONS. 



The Contour of the Bed of the Atlantic. — The Atlantic Ocean divided by a Series 

 of Ridges into Three Basins. — The Nature of the Bottom. — Pelagic Foraminif- 

 era. — Hastigerina Murrayi. — Volcanic Debris. — Products of the Decomposition 

 of Pumice. — The Distribution of Ocean Temperature. — Laws regulating the 

 Movements of the Upper Layers of the Atlantic. — Corrections of Six's Ther- 

 mometers. — Laws regulating the Movement of Water in the Depths of the 

 Atlantic. — The Doctrine of " Continuous Barriers." — The Distribution and 

 Nature of the Deep - sea Fauna. — The Universal Distribution of Living Be- 

 ings. — Causes modifying and restricting the Distribution of the Higher Forms. 

 — Relations of the Modern to the Ancient Faunas. — The Challengerida. — The 

 Density of Sea- water. — The Amount and Distribution of Carbonic Acid. — Of 

 Oxygen. 



Appendix A. — The General Result of the Chemical and Microscopical Examination 

 of a Series of Twenty Samples of the Bottom from the Observing Stations on 

 the Section between Teneriffe and Sombrero. 



Appendix B. — Table showing the Amount of Carbonic Acid contained in Sea-water 

 at Various Stations in the Atlantic. 



Appendix C. — Table showing the Relative Frequency of the Occurrence of the Prin- 

 cipal Groups of Marine Animals at Fifty -two Stations at which Dredging or 

 Trawling was carried to Depths greater than 2000 Fathoms. 



It is, of course, impossible at this stage of the work, while 

 the great bulk of the observations are still unreduced, while 

 the chemical analyses are ovl\j commenced, and there has not 

 been time even to unpack the natural -history specimens, to 

 give any thing like a detailed account of the additional data 

 which have been acquired by the Challenger expedition, or of 

 their bearings upon the various problems of physical geogra- 

 ph3^ Still, from the presence of a competent scientific staif 

 on board, a good deal was done during the voyage ; and certain 



