Prof. Tyndall on the History of Negative Fluorescence. 53 



In the presence of these published facts, which, as far as I can 

 see, were known, to me before the name of Dr. Akin was ever asso- 

 ciated with a physical inquiry, will it be believed that I needed 

 this gentleman's " ideas " to inform me what I was to do with 

 the obscure radiation from the electric light ? From Dr. Akin, 

 directly or indirectly, I never derived the fragment of an idea 

 for the work that I have accomplished. My work would have 

 been far more completely done, by this time, had he never existed. 

 His value to me has been purely negative, and that to an extent 

 little dreamt of by the readers of the Philosophical Magazine. 

 The real fact, moreover, is, that ten months ago I performed the 

 thankless task of communicating my ideas to Dr. Akin. I then 

 told him that a solution of iodine, in a rock-salt cell, would ena- 

 ble him to stop the solar light with the least possible detriment 

 to the purely thermal rays. I urged him to try the experiment ; 

 but he objected that rock-salt plates sufficiently large could not 

 be obtained. " Bring your cell near the focus," I replied, " an# 

 you will not require large plates/' He rejoined that the plates 

 would be destroyed by the heat ; I doubted this, but he finally 

 silenced me by the remark, that he had been actually led to try the 

 solution of iodine by what I had stated in my book regarding it, 

 but that it would not answer. It is the use which, to his know- 

 ledge, I have recently made of this very substance that has 

 roused his ire, and impelled him to the unwarrantable attack 

 which he has made upon me in the last Number of the Philoso- 

 phical Magazine. 



The true motives of that attack do not at all appear upon the 

 face of it ; and this leads me to remark that it is the absence of 

 a frank and open bearing, on the part of this gentleman, which 

 has created difficulties between him and me. In fact, had either 

 of us been other than he is, all difference might have been avoided. 

 If I had been suspicious, I should have kept him at a distance ; 

 if he had been outspoken, we should have understood each other. 

 There are words placed between inverted commas, in his " Note 

 on Ray- transmutation," which no reader of the Philosophical 

 Magazine can understand — the meaning of which is known 

 to Dr. Akin and myself alone. For instance, the words " that 

 very subject," and the word "attack" are extracted from a 

 private letter, already referred to, as written to Dr. Akin from 

 the Isle of Wight. He possesses that letter ; / now expressly 

 ask him to publish it in extenso. It is a short note, which will 

 more clearly reveal the spirit in which I proposed to deal with 

 this question, than anything I can now say. 



At the very time when the proofs of my paper "On Lumi- 

 nous and Obscure Radiation," on which he has bestowed his 

 malevolent criticism, reached my hands, Dr. Akin was con- 



