Dr. C. K. Akin on Ray -Transmutation. 559 



field, but what they are capable of doing that is new. It may be 

 difficult to decide which habit is of more importance — to study the 

 literature of the past, or to attend to the publications of the pre- 

 sent day. Much waste of thought would be prevented by either ; 

 but the latter proceeding has the additional advantage of pre- 

 venting the necessity of such explanations as those preceding, 

 extorted by the natural obligations of self-defence and the 

 defence of right*. 



5. Prof. Tyndall states (Phil. Mag. S. 4. vol. xxviii. p. 338):— 

 " The rendering of metals incandescent by obscure rays has not 

 yet been accomplished. This is a question on which Dr. Akin 

 has been engaged for some years, and it is not my intention to 

 publish anything relating to it until the very promising arrange- 

 ments which he has devised have had a sufficient trial" j\ Regard- 

 ing this statement, I think it useful to publish the substance of 

 a letter lately addressed by me to the President of the British 



* Merely as an illustration of what has been stated above regarding for- 

 getfulness, I shall mention the following instance. 



In the paper commented on in this Note, Prof. Tyndall says, amongst 

 other things (p. 332) : — " In solid metals augmented temperature intro- 

 duces waves of shorter periods into the radiation. It may be asked, 

 ' What becomes of the long obscure periods when we heighten the tem- 

 perature ? Are they broken up or changed into shorter ones, or do they 

 maintain themselves side by side with the new vibrations ? ' The question 

 is worth an experimental answer." Now that question had been practically 

 answered by Prof. Draper, as long ago as 1847. He said (Phil. Mag. S. 3. 

 vol. xxx. p. 350 : — " It is to be remarked that, while the more refrangible 

 end [of the spectrum] undergoes a great expansion, the other extremity 

 exhibits a corresponding though a less change .... arising from the in- 

 creased brilliancy of the light ... [as the temperature rises]." No doubt, 

 Prof. Tyndall has read the paper from which these latter passages are 

 taken, and which has generally been considered (and more especially so by 

 Melloni) as of great importance. But Prof. Tyndall has evidently forgotten 

 the fact, or else he would certainly have mentioned it; and yet it would be 

 impossible for him to assert that his own query regarding the invisible rays 

 would have been suggested to him had he not previously read the above 

 statement concerning the visible rays. In a similar manner, it would not 

 be difficult to trace back what Prof. Tyndall says concerning the light and 

 heat of a candle (/. c. p. 33D) to what, it is at least likely, was its original 

 source. 



t I must be allowed to express here a doubt whether Sir II. Davy, for 

 instance, or any other predecessor of Prof. Tyndall at the Royal Institu- 

 tion, having read in a public print that two persons were engaged in making 

 researches upon a certain subject with the aid and sanction of the British 

 Association, would have chosen " that very subject " " for attack " some 

 little time after. Nor do I believe that Davy or Young, having publicly 

 pledged themselves not to " publish " anything relating to the subject 

 till a certain contingency, would have meanwhile proceeded with it pri- 

 vately ; at all events they would not, as soon as they had obtained what 

 might turn out to be the desired result, have rushed off to repeat (and thus, 

 to all intents, publish) the experiment before their " colleague " — the sheets 

 in which that pledge was published being then scarcely dry, and the con- 

 tingency referred to as yet unaccomplished. 



