54 Prof. Tyndall on the History of Negative Fluorescence. 



versing with me at the Royal Institution. I broke the cover 

 in his presence, and, finding that it contained a duplicate proof, 

 handed one directly to him; for I wished him to see what I 

 had there said regarding himself. He read that proof before I 

 did ; and though this occurred ten or twelve days prior to the 

 publication of the paper, or about the 18th of October, the first 

 murmur of his dissatisfaction comes, at once to the public and to 

 me, in the December Number of the Philosophical Magazine. It 

 is not, I believe, the rule of courtesy in this country to publish 

 private correspondence without some mutual understanding, much 

 less to garble it. But I trust I do not oifend against this rule 

 by stating that twenty-four hours before Dr. Akin's article " On 

 Ray-transmutation " met the public eye, I received a friendly note 

 from that gentleman, acknowledging some trifling civilities which 

 it had been in my power to show him, but not containing the 

 slightest intimation of his attack. During the last days of Octo- 

 ber, and the early part of November, there had passed between 

 Dr. Akin and myself a somewhat voluminous correspondence, 

 which, when it ceased to be useful, I was obliged to end, with 

 an understanding, however, that it should be renewed as soon as 

 hisfeelings had calmed down. I rejoiced to think that the friendly 

 communication above referred to was an evidence that the 

 period of calmness had arrived, and I resolved, if such were 

 the case, to give him an opportunity of associating his name 

 with the experiments I had been making on the invisible 

 radiation of the electric light. The vanity of this resolve is 

 now demonstrated. The words " will now realize and ' publish ' 

 a discovery," used in the last page of Dr. Akin's article, are 

 also quite characteristic. No one could infer from these words 

 that I had actually, out of consideration for him, waived all 

 right of making my researches known until the 3rd of November 

 1865, for the express purpose of giving him the chance of prior 

 publication. I may add that when I entered into this volun- 

 tary engagement, which, by his own deliberate act, he has now 

 dissolved, I had no notion that Dr. Akin had any doubt of his 

 ability to give his attention to scientific researches. 



The following brief summary may, perhaps, spare him the 

 time and trouble of further criticism regarding the " inconclu- 

 siveness " of my experiments. 



1. By sending the beam from the electric lamp through a 

 sufficiently thick layer of iodine dissolved in bisulphide of carbon, 

 the luminous portion of the radiation may be entirely intercepted, 

 and the non-luminous almost entirely transmitted. 



2. The invisible rays, suitably converged, form, at their place 

 of convergence, a clearly defined, but perfectly invisible image 

 of the coal-points whence the rays emanate. 



