isroTXCiES oif zmhezmzohr-s. 



On the Conditions which Determine the Presence or Absence 

 of Animal Life on the Deep-Sea Bottom. By Dr. W. B. 

 Carpenter, F.B.S. 1 



THE foundation of Geological Science must be based upon a study 

 of the changes at present going on upon the surface of the earth, 

 including the depths of the sea. This is the distinctive feature of 

 modern Geology. Until recently nothing was really known of the 

 depths of the ocean ; but, owing to improved methods of sound- 

 ing, the bottom of the sea has been reached in so many places, that 

 we may feel tolerably sure that its depth seldom exceeds four miles. 

 Becent statements regarding an extraordinary depth off the coast of 

 Japan are, most probably, due to an error similar to that which 

 formerly represented the Straits of Gibraltar as unfathomable — an 

 error caused by the carrying-out of the sounding-line in a strong 

 surface-current. The general depth of the Atlantic does not exceed 

 three miles, though, as an exception, the "Challenger" has recently 

 attained 3800 fathoms in a hole 100 miles north of St. Thomas. 

 As an additional proof that this was a true sounding, both the pro- 

 tected thermometers came up crushed. 



The temperature of deep water has only lately been ascertained 

 with accuracy, the earlier attempts having been vitiated by the error 

 arising from pressure. Of the older attempts to ascertain the tem- 

 perature of the deep strata, that devised by Lenz in the second voyage 

 of Kotzebue, though fearfully laborious, gave results that corre- 

 spond most closely with the " Challenger's " ; a fact in scientific 

 annals which has been lately dug out by Prof. Prestwich, and by him 

 brought to the notice of the lecturer, who found his own conclusions 

 — made in entire ignorance of those of Lenz — thus singularly con- 

 firmed. The conclusions to be drawn from a study of these tem- 

 peratures point towards a deep flow of polar water towards the 

 Equator, unrestricted, as regards the Atlantic, towards the south, 

 but limited in the direction of the North Polar area, where there are 

 two principal channels : the one between Greenland and Iceland, 

 the other between the Faroe Islands and the 100-fathom line of 

 North-west Europe, on which platform the British Islands repose. 

 This latter is the " Lightning " channel, the scene of the lecturer's 

 first explorations, the study of which led to his view of the exist- 

 ence of two opposite flows in the great oceanic area, quite irrespective 

 of any one current. In this channel it was found that there was a 

 superficial warm stream and a deep cold stream ; and that within a 

 vertical space of 50 fathoms a most marked difference of temperature 

 is suddenly encountered ; whilst, as regards horizontal distance, tem- 

 peratures of 29^° F. and 43° F. have been obtained at the same depth 

 in places not 20 miles apart. These facts mean that there are two 

 distinct movements of water, just as a striking difference in the 

 temperature of the atmosphere indicates a change of wind. Hence, 

 speaking with reference to the " Lightning" channel, it is clear that 



1 Being the substance of a Lecture delivered before the Geologists' Association, on 

 Deeember 4th, 1874. Henry Woodward, Esq., F.R.S., President, in the Chair. 



