829 



from sea- water owing to the escape of carbonic acid gas, — are facts 

 clearly proving that carbonate of lime is as a constituent of sea- water 

 neither rare of occurrence, nor unimportant in the oeconomy of na- 

 ture, inasmuch as the phsenomena alluded to, — the one destructive, 

 the other restorative, — have been observed in most parts of our 

 globe where geological inquiry has been instituted. 



Reflecting on the subject, it seemed to me desirable to ascertain 

 whether carbonate of lime as an ingredient of sea-water is chiefly 

 confined to the proximity of coasts, or not so limited enters into 

 the composition of the ocean in its widest expanse. 



On a voyage from Barbados in the West Indies to England in 

 November last (1848), I availed myself of the opportunity to make 

 some trials to endeavour to determine this, the results of which I 

 shall now briefly relate. 



First, I may mention that water from Carlisle Bay in Barbados, 

 tested for carbonate of lime, gave strong indications of its presence ; 

 thus a well-marked precipitate was produced by ammonia, after the 

 addition of muriate of ammonia in excess, that is, more than was 

 suflicient to prevent the separation of the magnesia which enters so 

 largely into the composition of sea-water ; and a like effect was pro- 

 duced either by boiling the water so as to expel the carbonic acid, 

 or by evaporation to dryness and resolution of the soluble salts. 



On the voyage across the Atlantic, the test by means of ammonia 

 and muriate of ammonia was employed, acting on about a pint of 

 water taken from the surface. The first trial was made on the 15th 

 of November, when in latitude 20° 30' N., and longitude 63° 20' W., 

 more than a hundred miles from any land ; the result was negative. 

 Further trials were made on the 22nd of the same month in lat. 

 32° 53', long. 45° 10' ; on the 24t.h, in lat. 36° 23', long. 37° 21' ; on 

 the 25th, in lat. 37° 21', long. 33° 34'; on the 26th, in lat. 38° 28', 

 long. 30° 2' ; on the 27th, when off" Funchal of the Western Islands, in 

 lat. 38° 32', long. 28° 40', about a mile and a half from the shore, the 

 water deep blue, as it always is out of soundings: in all these instances 

 likewise the results were negative ; the transparency of the water 

 was nowise impaired by the test applied. The last trial was made on 

 the 3rd of December, when in the Channel off" Portland Head, about 

 fifteen miles ; now, slight traces of carbonate of lime were obtained, 

 a just perceptible turbidness being produced. 



The sea-water from Carlisle Bay, the shore of which and the ad- 

 joining coast are calcareous, yielded about 1 per 10,000 of carbonate 

 of lime, after evaporation of the water to dryness, and the resolution 

 of the saline matter. A specimen of water taken up on the voyage 

 off" the volcanic island of Fayal, about a mile from land, yielded a 

 residue which consisted chiefly of sulphate of lime, with a very little 

 carbonate of lime,— a mere trace ; acted on by an acid it gave ofi" 

 only a very few minute air-bubbles. A specimen taken up oif Port- 

 land Head, about fifteen miles, yielded on evaporation and resolu- 

 tion of the saline matter only a very minute residue, about '4 only 

 per 10,000; it consisted in part of carbonate and in part of sulphate 

 of lime. 



