30 On the Depth and Saltness of the Ocean. 



polar circle. These are, it is true, but conjectures derived 

 from detached and isolated trials, and may not be confirmed 

 by future and well-conducted experiments ; they are only ad- 

 duced here to shew the field open to investigation, and to 

 prompt to measures that the Association may deem necessary 

 to secure results. A well-directed series of experiments taken 

 with the imperfect means we now have, could not fail to 

 make us acquainted with the submarine valleys and ridges 

 which traverse our globe, and, in time, give us sections of the 

 beds of the ocean. There are many opportunities enjoyed by 

 the commanders of our men-of-war that might be taken ad- 

 vantage of whilst proceeding to and returning from the dif- 

 ferent foreign stations ; and, I make no doubt, that these 

 would be readily authorised by the distinguished gentleman 

 who now presides over the naval service. All that is required 

 is, for this Association to take some measures to forward this 

 subject, and to point out positions at which it would be most 

 desirable to obtain results. If those who have the direction of 

 foreign navies could be induced to join, we should be enabled, 

 in a very few years, to exhibit complete sections of the oceans 

 and seas, and full investigations into the phenomena con- 

 nected with the ocean. 



Although the actual depth of the ocean has not yet been 

 successfully determined, the numerous trials have resulted in 

 determining satisfactorily its mean temperature and density. 

 Its mean temperature is nearly 39^-5' ;* and, according to 

 Captain Ross's experiments, the zone of mean temperature 

 lies between the parallel of 54" and 60^ of south latitude, not 

 only at the surface, but to as gi'eat a depth as the ocean has 

 been penetrated. Future trials will, in all probability, re- 

 duce it to narrower limits ; its position in the northern hemi- 

 sphere remains yet to be ascertained. This mean tempei'a- 



* I am aware that several distinguished navigators and others have reported 

 different results ; among them, Mr Lenz even places it down to 3G and 37 , 

 which they report ha\ ing met with in the tropics at nearly 1000 fathoms. Prom 

 our own experiments, and from those of many others, I cannot but believe that 

 some error has occurred. 1 am well satisfied that so low a temperature will not 

 be obtained within the tropics at any depth, unless through the agency of sub- 

 marine currents. 



