602 Mr. J. Y. Buchanan on Chemical Work 



A large number of observations on the specific gravity of the waters at 

 the bottom and intermediate depths have been made. In a preliminary 

 report like the present it would be out of place to enter upon the discus- 

 sion of so extensive a subject, even did the time at my disposal admit of my 

 attempting it. I therefore content myself with giving the numerical results. 

 It is to be hoped that in the homeward cruise through the Atlantic a 

 more complete series of observations in this direction may be obtained, as 

 those obtained on the way out were only sufficient to show that this ocean, 

 and especially its northern part, differs greatly from the rest of the 

 world-sea in density, as it does in temperature and in many other parti- 

 culars. As a general rule, in both oceans between the parallels of 40° N. 

 and 40° S. the specific gravity (reduced to 15°*56 C.) is greatest at or 

 near the surface, and decreases more or less regularly until a minimum 

 is reached, generally about 400 fathoms from the surface, when there is 

 a slow rise, the bottom-water being rather heavier. This general Jaw 

 obtains in the Pacific and in the South Atlantic; but from the few 

 observations obtained in the North Atlantic, there are indications of a 

 departure from it. Although in the case of surface-water the variations 

 of specific gravity with latitude are very considerable, more especially in 

 the Atlantic, the water below 200 fathoms presents great constancy, the 

 variations being comparable with those of the temperature at the same 

 depths. In intertropical regions, and generally where there exist alter- 

 nating wet and dry seasons, there are usually more than one maximum 

 and minimum in the series between the surface and the bottom. How 

 long it takes in quiet seas for fresh water to diffuse downwards in the 

 sea, will be seen by inspection of the results obtained on the 22nd 

 February, 1875, above referred to, when about 80 miles off the mouth of 

 one of the large rivers of New Guinea, and the sea covered with drift- 

 wood. The specific gravity was at the surface 1*02537 ; at 10 fathoms, 

 1-02578; at 20 fathoms, 1-02584; at 40 fathoms, 1-02594; at 50 

 fathoms, 1*02636 ; and at 100 fathoms, 1*02658, where it obtained its 

 maximum, the temperature being sensibly the same down to 50 fathoms, 

 namely from 28° C. to 28°*4 C. 



Observations on the Carbonic Acid contained in Sea-water. 



The carbonic acid when boiled out of the water is received by baryta- 

 water of known strength ; its consequent loss of alkalinity is measured 

 by hydrochloric acid of corresponding strength. Having observed that 

 the presence of sulphates in sea-water is one of the potent agents in 

 the retention of the carbonic acid*, I always add 10 cub. centims. 

 of a saturated solution of chloride of barium to the water before 

 commencing the operation. This facilitates greatly the liberation of 

 the carbonic acid, and also causes the water to boil tranquilly, even 

 to dryness, without showing any tendency towards bumping. The 

 * Proc. Eoy. Soc. 1874, vol. xxii. pp. 483-495. 



