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On the Specific Gravity of the JFater of the Sea off the Coast of 

 British Guiana. By JOHN Davy, M.D., F.R.S., Lond. 

 & Ed., Inspector-General of Army Hospitals, ttc. Com- 

 municated in a letter addressed to Professor Jameson. 



My dear Sir, — Conceiving that some useful results might 

 be obtained by determining the specific gravity of sea-water 

 at different distances from the land, along the shores of which 

 large rivers pour out their waters, such as that of British 

 Guiana, on a return voyage which I recently made from that 

 Colony, viz. — in the first week in June, — I had specimens of 

 water taken up for the purposed trial. They were put into 

 phials provided with glass stoppers, and their specific gravity 

 was determined after arrival in Barbadoes in the ordinary way, 

 using a very delicate balance : each specimen was numbered 

 at the time it was obtained. 



No. 1 was taken from the shore at George Town, where 

 the Demerara river meets the sea, and where the water is 

 only just perceptibly saline. Its specific gravity atSG"" Fahr. 

 compared with rain-water of the same temperature, was 

 10036 to 10000. 



No. 2 taken up, where the mail steamer, in which I em- 

 barked, was at anchoi', about a quarter of a mile from the 

 shore, was of specific gravity, 10'991. 



No. 3, from about 11 miles from the shore was of specific 

 gravity, 10-210. 



No, 4, about 19 miles off, was of specific gravity, 10-236 



10-24:95 

 10-236 

 10-2495 

 10-258 

 10-266 



This last mentioned specific gravity was of water taken up 

 when the sea had acquired, or nearly so, the blue colour of the 

 ocean, and is a near approach to that of sea-water generally in 

 the West Indies. The highest that I have ascertained hav- 

 ing been 10273, which was of water from of the coast of 



