Prof. Tyndall on the History of Negative Fluorescence. 47 



1 Reader ' newspaper. Immediately afterwards a letter, ad- 

 dressed to me by Dr. Akin, was forwarded to me, in which he 

 drew my attention to what he had previously written, and 

 expressed a desire to see me. I replied to this letter with all 

 goodwill, and my answer, I have reason to believe, is still in the 

 hands of Dr. Akin. After my return to town he called upon 

 me, and among other things directed my attention to a report 

 in the 'Reader' of the 26th of September 1863. In this 

 report I found the following passages: — "The glow of a 

 platinum wire in a Bunsen's gas-burner, of carbon particles in 

 a candle-flame, and of lime in the oxyhydrogen-flame, and no 

 less so the phenomena of coloration to which the introduction 

 of substances capable of vaporization gives rise in ordinary gas- 

 flames, in the opinion of the author, constitute examples of ray- 

 renovation or transmutation in statu nascenti (so to speak) of the 

 rays;" and again, with reference to the oxy hydrogen-flame, "it 

 admits of little doubt that the Newtonic [visible] and Ritteric 

 [ultra-violet] rays engendered by the introduction of lime into 

 the flame, arise from a transmutation of Herschellic [ultra-red] 

 rays in the very act of transmission." 



On being made acquainted with these expressions, I did not 

 halt to criticise the grounds of Dr. Akin's "opinion," but I at 

 once wrote the following note, which appeared in the next Num- 

 ber of the ' Reader ': — 



" Athenaeum Club, April 9, 1864. 

 "Through the kindness of its author, I have this day become 

 acquainted with Dr. Akin's communication to the 'Reader' of 

 the 26th of December 1863. From conversation with Prof. 

 Stokes, I had obtained a general notion of the experiments in 

 which Dr. Akin has been for some time engaged, but I now 

 learn that on one of the points touched upon in the report of my 

 last investigation — the proposed explanation, namely, of the 

 glowing of a platinum wire in a hydrogen-flame — he has antici- 

 pated me by several months. 



"John Tyndall." 

 I afterwards learned that Dr. Akin did not wait for me to set 

 matters right, but had promptly put in his own claim on the 

 2nd of April, 



I have thus shown how the idea of negative fluorescence 

 entered my mind; I have explained the nature of my mis- 

 take in supposing that I was the first to recognize, in the 

 heating of a platinum wire in a hydrogen-flame, a change of 

 period, and I have described the reparation made when Dr. Akin's 

 relation to the subject became known to me. It never occurred 

 to me to criticise the scientific method by which Dr. Akin 

 arrived at his conclusions. I believed them to be correct, and 



