58 Mr. W. Crookes on the Discovery of the Metal Thallium. 



had discovered a green band in the spectrum without knowing 

 that I had observed the same fact fifteen months before. He 

 mentioned that I had shown this green band to be due to the 

 presence of a new element, to which I had given the name of 

 thallium, and added that the small quantity of material on which 

 I operated did not admit of my isolating the element and 

 ascertaining its true nature. 



In a communication made to the Societe Imperiale at Lille 

 on the 16th of May, 1862*, he also described thallium to be a 

 metal, and, referring to my papers of 1861, stated that the black 

 powder which I regarded as thallium was nothing but sulphide 

 of thallium. 



In regard to this statement, I must, in the first place, point 

 out that M. Lamy entirely ignores the fact of my having exhi- 

 bited thallium as a metal on the 1st of May, 1862, and of having 

 then described it as a " heavy metal, reduced from its acid solu- 

 tions by zinc in the form of a dense black powder." The labels 

 in my case were unmistakeably clear and definite in their word- 

 ing ; the metallic nature of thallium was both stated and implied 

 by all of them ; they did not leave the least possibility for the 

 supposition that I considered thallium to be a metalloid ; and the 

 publication was in every respect as full as the reading of a paper 

 at a provincial scientific society. 



These, then, are the real facts of the case. As to the question 

 of priority, I would submit that there can be no doubt. Even 

 on the showing of M. Lamy and his friends, I was prior to him 

 in every step of the discovery. M. Lamy claims to have first 

 noticed the presence of the green band in the spectrum in April 

 1862 ; whilst I had discovered it thirteen months previously, and 

 published a description of the substance by which it was produced. 



M. Lamy claims to have isolated thallium in the interval 

 between the 2nd and the 16th of May, 1862, and states that he 

 for the first time exhibited the metal at Lille on the latter datef ; 

 whilst I isolated thallium in September 1861, and exhibited it as 

 a metal on the 1st of May, 1862. 



Still, M. Dumas, in reporting on the subject to the Academy, 

 has stated that the history of the discovery of thallium presents 

 two authentic dates — the 30th of March 1861, when Mr. Crookes 

 announced the existence of a new elementary substance, and the 



* Ann. de Chim. et de Phys. before quoted. 



f The following extract from the register of the proces-verbaux of the 

 Societe Imperiale des Sciences, de l'Agriculture et des Arts, at Lille, is 

 given by M. Lamy as the earliest notice of his discovery : — 



"At the meeting of the 16th of May, 1862, under the presidency of M. 

 Lamy, M. Lamy announced to the Society that he had succeeded in isolating 

 thallium by decomposing with a voltaic battery the yellow crystalline com- 

 pound of which he had spoken at the meeting on the 2nd of May." 



