467 



in 7000 grains of the liquid at 60^ F. This result was announced 

 to the British Association at its meeting for that year, and to this 

 Society in November. In 1849 these observations were repeated 

 with certain variations, to meet objections which had been raised to 

 my conclusions, but with the same result. In 1849 I communi- 

 cated to the British Association the results of a series of analyses, 

 demonstrating by a new method of inquiry the presence of fluorine 

 in the waters of the Frith of Forth, the Frith of Clyde, and the 

 German Ocean ; and in March 1850 I communicated to this So- 

 ciety an additional series of observations made in the same way, but 

 extended to the waters of the Irish Sea, of the Atlantic, and the 

 Mediterranean. This paper was accompanied by a letter from Pro- 

 fessor Forchammer of Copenhagen, testifying to the presence of 

 fluorine in the waters of the Baltic. In the summer of the same 

 year (1850) I returned to the analysis of blood and milk for fluorine, 

 feeling assured that still more decisive proofs of its presence in 

 both could be obtained by using a larger amount of material, and 

 subjecting it to a simpler process. Accordingly, employing in the 

 case of blood (which was that of the ox) 26 imperial pints, in the 

 case of milk 9 imperial pints, and in that of cheese 12 lbs., I was 

 able to etch glasses with the hydrofluoric acid evolved from them so 

 deeply that they might have been printed from, like copper plates. 

 The etched glasses were shown to the members of the Chemical and 

 Physiological Sections of the British Association, at its meeting in 

 Edinburgh in 1850, and the details of the process published in its 

 " Transactions," as well as in the Edinburgh Philosophical Journal for 

 October of that year.* In the spring of 1852, 1 again brought the 

 subject before this Society in a paper entitled " On two new Processes 

 for the Detection of Fluorine when accompanied by Silica ; and on 

 the presence of Fluorine in Granite, Trap, and other Igneous Bocks, 

 and in the Ashes of Recent andFossil Plants." (Read April 1 9, 1852.) 

 In the summer also of the same year, a communication, founded on 

 an application of these processes, was made to the Botanical Society 

 of Edinburgh, — " On the presence of Fluorine in the stems of Gra- 

 mineae, Equisetaceae, and other Plants, with observations on the 

 sources from which vegetables derive this element." In this com- 



* They are specially referred to in the English translation of Lehmann's 

 " Physiological Chemistry," by Prof. G. E. Day, vol. i., p. 425. Cav. Soc. Publ. 

 1851. 



