524 Royal Society : — 



of the Ocean, where the sea is so httle disturhed, would very sensibly 

 diminish it. It is also very sensibly less in the vicinity of the coast, 

 particularly when the latter is of a shoal character, as is the case 

 between the River Plate and the Strait of IMagalhaens, where the 

 whole extent is fronted by a bank having from 30 to 50 fathoms of 

 water. 



The mean specific gravity of the water of the South Pacific, con- 

 tained between the parallels of 10° and 40°, is 1026*48, and between 

 40° and 60° it is 1026- 13. 



" On the Existence of Silver in Sea-water." By Frederick Field, 

 F.C.S. 



In a paper published by ]MIM. Malaguti, Durocher, and Sar- 

 zeaud in the 'Annales de Chimie et de Physique,' xxviii. p. 129, 

 there is an account of the detection and estimation of silver in 

 sea-water. The authors suspected the existence of the metal from 

 the extensive diffusion of silver in the mineral kingdom, the conversion 

 of its sulphide into chloride by the prolonged action of soluble bodies 

 containing chlorine, and the solubility of chloride of silver in chloride 

 of sodium. The method pursued was by passing sulphuretted 

 hydrogen through large quantities of water, and also by fusing 

 the salts obtained by evaporation with litharge and subsequent cu- 

 pellation. 



As a solution of chloride of silver in chloride of sodium is instantly 

 decomposed by metallic copper, chloride of copper being formed and 

 silver precipitated, it appeared to me highly probable that the copper 

 and the yellow metal used in sheathing the hulls of vessels, must, 

 after long exposure to sea-water, contain more silver than they did 

 before ha^ang been exposed to its action, by decomposing chloride 

 of silver in their passage through the sea, and depositing the metal on 

 their surfaces. A large vessel, the ' Ana Guimaraens,' now under the 

 Chilian flag, was hauled down in the Bay of Herradura, near Coquimbo, 

 for the purpose of being repaired, and the captain obligingly furnished 

 me with a few ounces of the yellow metal from the bottom of the vessel. 

 The investigation was interesting, as the metal had been on for more 

 than seven years (an unusually long period), and the ship had been 

 trading up and down the Pacific Ocean all that time. The metal, 

 upon examination, was found to be exceedingly brittle, and could be 

 broken between the fingers with great ease. 5000 grs. were dissolved 

 in pure nitric acid and the solution diluted ; a few drops of hydro- 

 chloric acid were added, and the precipitate allowed to subside for 

 three days. A large quantity of white insoluble matter had collected 

 by that time at the bottom of the beaker. This was filtered off, 

 dried, and fused with 100 grs. pure litharge and suitable proportions 

 of bitartrate of potash and carbonate of soda, the ashes of the filter 

 also being added. The resulting button of lead was subsequently 

 cupelled, and yielded 2'01 grs. silver, or 1 lb. 1 oz. 2 dwts. 15 grs. 

 troy per ton. This very large quantity could hardly be supposed to 

 have existed in the original metal, as the value of the silver would be 

 well worth the extraction. It is to be regretted that the captain had 



