304 THE DEPTHS OF THE SEA. [chap. vii. 



There can be no doubt that this view, which of 

 late years has received almost universal acceptance, 

 is entirely erroneous. It has been shown by M. 

 Despretz, 1 as the result of a series of carefully con- 

 ducted experiments which have since been frequently 

 repeated and verified, that sea-water, as a saline 

 solution, contracts and increases steadily in density 

 down to its freezing-point, which is, when kept 

 perfectly still, about — 3°G7 C. (25° # 1 P.), and when 

 agitated -2°55 C. 



The temperature observations of Sir James Clarke 

 Hoss during his Antarctic voyage in 1810-41, 

 seemed to give support to the theory of a constant 

 temperature of 4°o C. for deep water, but these obser- 

 vations have as evidently been made with unguarded 

 instruments, as those of Sir John Hoss in 1818 with 

 instruments defended from pressure ; and although 

 I believe they must be taken as proving that in 

 high southern latitudes the surface temperature is 

 sometimes lower than the temperature of the water 

 at a considerable depth beneath, still the amount of 

 correction for pressure is uncertain, depending upon 

 the construction of the thermometers used, and in 

 any case it must reduce the difference considerably. 



A large number of thermometers of the ordinary 

 Ilydrographic Office pattern were sent out with us, 

 as I have alreadv mentioned, in the ' Lightning,' 

 and these were of course the instruments used by 

 Staff-Commander May for his temperature obser- 

 vations. There was an opportunity of testing these 

 thermometers, however, on the return of the vessel, 



Recherches sur le Maximum de Densitu des Dissolutions aqueuses. 

 Luc. cit 



