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Forth, and mentioned, that, in the preceding summer, he had found 

 it in deposits obtained during the evaporation of sea-water from the 

 Frith of Clyde, and the German Ocean. Professor Forchammer 

 had made similar observations on the Baltic, and had furnished Dr 

 Wilson with the account of them which follows. Before reading 

 this, he wished to add, that he had recently examined incrustations 

 from the boiler of a steam-vessel sailing between Liverpool and Dub- 

 lin, and similar deposits from the Canada Transatlantic steamer, and 

 H.M. war-steamer Sidon, which had been three years on the Medi- 

 terranean station. The different crusts were, without preliminary 

 treatment, except reduction to powder, heated with oil of vitriol, and 

 were found to yield an acid vapour which etched glass. Specimens 

 of glass, in illustration, were shewn to the Society. From these ob- 

 servations, Dr Wilson inferred the presence of fluorine in the Friths 

 of Forth and Clyde, in the German Ocean, the Irish Sea, the At- 

 lantic, and the Mediterranean. He then proceeded to read Profes- 

 sor Forchammer's communication, which follows. It is dated, Copen- 

 hagen, 20th December 1849. 



Abstract of a Paper by Professor Forchammer, on the rarer Sub- 

 stances which occur in Sea-water. 



Fluorine and Phosphoric Acid. 

 100 lb. of sea- water, as it occurs in the Sound, near Copenhagen, 

 of which the average quantity of salts is between 2 and 2 J per 

 cent., was evaporated. When the solution was so concentrated that 

 it began to deposit salt, it was, without filtering it, mixed with an 

 excess of ammonia, and the precipitate collected and washed. The 

 whole precipitate which contains carbonate, sulphate, and phosphate 

 of lime, fluoride of calcium, silica, and magnesia, was redissolved in 

 muriatic acid, which left the greater part of silica undissolved ; the 

 solution was mixed with muriate of ammonia, and a second time 

 precipitated by an excess of ammonia. This precipitate from 100 lb. 

 of sea- water weighed 3' 104 grains, and consisted of phosphate of 

 lime and fluoride of calcium. It was divided into two equal parts, 

 of which the one was in a platina crucible, mixed with concentrated 

 sulphuric acid, and allowed to act on a slip of glass, covered with wax, 

 in which some words were scratched with a copper needle. The 

 glass was most decidedly etched, but the words appeared more clear 



