Iviii PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



" that all climatal inferences drawn from the number of northern 

 forms in strata containing assemblages of organic remains are 

 fallacious, unless the element of depth be taken into considera- 

 tion " *. 



I mention these observations (made many years since, and which 

 of late have generally been taken into account in all geological 

 inquiries) to show that geologists have still to be guided by the 

 same primary natural-history rules, which have lately received 

 so wide an extension and application in these recent deep-sea 

 dredgings. 



The mistake made by Edward Forbes was his assigning the 

 too narrow limit of 1800 feet in vertical depth as the probable zero 

 of animal life in the ocean. Dr. Wallich afterwards extended the 

 probable limits of life to 15000 feet ; and now the important re- 

 searches of Carpenter, Jeifreys, and Thomson show that it must in 

 all probability be carried very much lower, as they have found a 

 highly organized fauna living in abundance at the vast depth of 

 14,610 feet, and no indication of an approach to the zero of life. 

 It had, in fact, been long felt that the proposition involved in these 

 bathymetrical limits was open to question. 



The many interesting problems connected with the temperature 

 and currents of the ocean have often engaged attention since the 

 early part of this century. It was one of the subjects respecting 

 which a large amount of data was collected on the several scientific 

 naval expeditions sent out by the French Government between 1820 

 and 1840. Humboldt states f that he showed in 1812 that the 

 low temperature of the tropical seas at great depths could only be 

 owing to currents from the poles to the equator. 



D'Aubuisson, in 1819, also attributed the low temperature of the 

 sea at great depths at or near the equator to* the flow of currents from 

 the poles X' 



Lenz§, in 1831, gave the results of some experiments he had 

 made at great depths in the ocean, and concluded that between the 

 equator and 45° of lat. the temperature decreases regularly to the 

 depth of 6000 feet, when the decrease becomes insensible. The 

 lowest temperature he recorded was 36° Fahr. 



* Edinb. New Phil. Journ., April 1844. 



t Fragmens de G6ol. et de Climatol. Asiat. 1831. 



I Traite de G6ognosie, p. 450. 



§ Edinb. Journ. of Science, vol. vi. p. 341. 



