350 Dr George Wilson on the Detection of Fluorine 



appeared to be so scanty a constituent of plants, was its 

 occurrence along with silica, which makes its recognition 

 very difficult. I had given up, accordingly, all hopes of satis- 

 factorily demonstrating its wide distribution, till better pro- 

 cesses than are at present in use, were devised for its detec- 

 tion when accompanied by silica. 



For the same reason I have thought it hitherto useless to 

 endeavour to trace back fluorine from the plants, animals, 

 natural waters, and the more accessible strata which are the 

 main seats of life at the present day, to those earlier rocks 

 and geological formations which have furnished our soils, 

 and have contributed the chief soluble matters which are 

 found in the lakes, rivers, and seas of the globe. The more 

 ancient rocks abound in silica, and, with our present pro- 

 cesses, the prospect of discovering fluorine in trap and simi- 

 lar siliceous masses, was not encouraging. A representation, 

 however, from Professor Jameson, as to the importance at- 

 taching to the detection of fluorine in the most ancient rocks, 

 led me to reconsider the geological and mineralogical interest 

 which the inquiry possessed ; and within the last six weeks 

 I have put in practice two methods of investigation, which I 

 shall now explain. 



The processes at present in use for the separation of fluo- 

 rine from silica, are in many respects satisfactory ; but they 

 imply the rejection of glass apparatus, and the use of vessels 

 of platina, which, from their costliness, cannot be employed 

 of any considerable size, and, from their opacity, render the 

 observation of phenomena occurring within them impossible. 

 They are thus inadmissible for operations where large quan- 

 tities of materials must be dealt with : and to the impossibi- 

 lity of employing glass and porcelain vessels, must be largely 

 attributed the comparatively limited extent of our informa- 

 tion as to the distribution of fluorine. 



The following processes, which, in the meanwhile, are 

 offered only as qualitative (although I hope to succeed Jn 

 rendering the second of them quantitative), may be carried 

 on in the ordinary glass and porcelain vessels of the labora- 

 tory, and admit of everything visible being observed. They 

 are applicable to all siliceous compounds or mixtures contain- 



