1862.] 151 



mitting to this Society. I trust that, under these circumstances, I 

 may be pardoned for bringing before the Royal Society an incomplete 

 account of this new element. 



The occurrence of a brilliant green line in some selenium residues, 

 whilst examining them for tellurium, led me first to suspect the 

 presence of a new element. This had been derived from a con- 

 siderable quantity of the seleniferous deposit from the sulphuric 

 acid manufactory at Tilkerode in the Hartz Mountains, which had 

 been kindly placed at my disposal by Professor Hofmann ; and the 

 residue was that left behind on distilling the selenium which had 

 been prepared from the deposit by appropriate chemical treatment. 

 The processes through which it had passed limited the elements 

 which could by any possibility be present to some half dozen ; and 

 as I was pretty confident that none of these presented in the spectro- 

 scope the phenomenon of a single bright-green line, it became of 

 interest to investigate the subject further. In March 1861* I was 

 enabled to announce definitely that the green-line substance was 

 decidedly a new element, and that from some of its reactions it was 

 probably a high member of the sulphur, selenium, and tellurium 

 group, although I hesitated to assert this positively. The paper 

 alluded to contained a sufficient number of the reactions of this 

 body to enable me to prove chemically, as well as optically, that I 

 was dealing with a new element possessing well-defined characters. 

 Pursuing the investigation, I was enabled in the following Mayf to 

 give a further account of this body, and to propose for it the name 

 of Thallium (symbol 77), from the Greek 0a\\os, or Latin thallus, 

 a budding twig, a word which is frequently employed to express 

 the beautiful green tint of young vegetation, and which I chose on 

 account of the green line which it communicated to the spectrum 

 recalling with peculiar vividness the fresh colour of early spring. 

 In the same note I gave the localities and description of several 

 minerals in which I had found the element, and also a method of 

 extracting it from them in a pure state. Considering that I had 

 sufficiently announced the discovery in these papers, which were 

 republished in nearly every chemical journal in Europe, I turned my 



* Philosophical Magazine, S. 4. vol. xxi. p. 301 ; and Chemical News, vol. iii. 

 p. 194, March 30, 1861. 

 t Chemical News, vol. iii. p. 303, May 18, 186L 



