the History of Calcescence. 139 



the f Reader ' of April 2, 1864: — "I profit by this opportunity 

 to call your attention to your report of Prof. TyndalFs late lec- 

 ture at the Royal Institution. . I suppose it was only by inad- 

 vertence that you said, l such a change of period [or of invisible, 

 less refrangible, into visible rays], Prof. Tyndall believes, occurs 

 when a platinum wire is heated to whiteness by a hydrogen 

 flame/ &c. ; for in your own columns of September 26, 1863, 

 that explanation, communicated by me for the first time to the 

 British Association last year at Newcastle, was published in my 

 name, — a fact which I cannot but believe Prof. Tyndall has 

 referred to." As an afterthought, and as an act of courtesy to 

 Prof. Tyndall, I wrote to him, a day or two after, a private note, 

 enclosing a set of proof-sheets of my paper on Ray-transmuta- 

 tion, then printing in the Reports of the British Association. 

 In answer to that note, I received a letter from Prof. Tyndall, 

 dated from the Isle of Wight, in which he observed on the " sin- 

 gular coincidence of thought" that had arisen between us, and 

 stated that " the piece of work which he had set before him for 

 attack on his return" to town was a series of experiments on "that 

 very subject " that engaged my own attention. I was somewhat 

 astonished at this latter statement ; for, Prof. Tyndall having read, 

 as he himself informed me, the article on " Calcescence " in the 

 * Saturday Review/ was aware that the British Association had 

 confided to Mr. Griffith and myself the task of executing the 

 experiments, for which I had submitted the plans. As to the 

 "coincidence," real or supposititious, between Prof. TyndalPs 

 "thoughts" and mine, it could extend only to the explanation of 

 the origin of lime-light ; and Prof. Tyndall neither then nor has 

 he since ever stated that, before reading of my own method in 

 the ' Saturday Review/ he had planned any experiments on cal- 

 cescence similar to those I had submitted to the British Associa- 

 tion. Others, before both myself and Prof. Tyndall, had thought 

 that they had recognized phenomena evincing "negative fluores- 

 cence," and yet were unable to devise, for the purpose of proving 

 its existence, methods analogous to those adopted in the produc- 

 tion of fluorescence. That Prof. Tyndall had guessed for him- 

 self, or perhaps but remembered, the explanation of lime-light, 

 could form no right on his part to interfere with the experiments 

 I had devised, and was then engaged in working out by authority 

 of the British Association. However, Prof. TyndalFs letter 

 being on the whole written in a friendly and courteous tone, and 

 knowing the value of a conciliatory spirit, I went to see him a 

 few days after, by appointment, at the Royal Institution. Prof. 

 Tyndall then spontaneously stated to me that he wanted to act 

 towards me in an "honourable and gentlemanly "manner, and that 

 he would do what was "most pleasing" to me. At the same time, 



