the History of Calcescence. 147 



fee.) I had caused to be constructed a peculiar diaphragm for the 

 express purpose of containing iodine in solution, and I had made 

 those observations on the spectrum of that solution which I have 

 adverted to in the Philosophical Magazine for December 1864. 

 Prof. Tyndall asks whether it will be believed that he needed my 

 " ideas w to inform him what he was " to do with the obscure 

 radiation from the electric light ? " Why should it not be be- 

 lieved ? Every one knew that the invisible part of the radiation 

 of the sun is calorifically powerful — at least to the same extent 

 as Prof. Tyndall had shown that of the electric light to be by 

 the experiments to which he refers in his last paper. Every one 

 who had read Melloni's papers knew also that, by means of black 

 glass, the Herschellic rays may be separated from the Newtonic ; 

 and yet nobody knew what he was " to do " with the obscure radia- 

 tion of the sun. In the article published in the ' Saturday Review ' 

 the solution proposed by me for the problem which I had indi- 

 cated was compared with the solution proposed in the case of 

 " Columbus's egg ; " and as in that case, so also in mine, it is 

 easy to say, ex post facto, that anyone might have found the 

 solution, had he but bethought himself of it. 



4. As regards Prof. TyndalFs attempted criticism of my pub- 

 lished papers on the subject of calcescence, to which I have now 

 replied, I might have perhaps saved myself the trouble of an- 

 swering it. One of the Secretaries of the Royal Society wrote 

 to me, after reading those papers, that they showed " a perfect 

 mastery" of the subjects treated of; and relying upon this 

 judgment, I could have afforded to contemn Prof. TyndalFs ad- 

 verse opinions. I now have to reply to those statements of Prof. 

 Tyndall which concern more my person than my writings. 



Prof. Tyndall taunts me with " sitting down and proposing 

 experiments which may, or may not, be capable of realization. At 

 all events if this be done at all, it ought to be done in a mag- 

 nanimous spirit/' and not " with a view to mounting the high 

 horse of Neptune." This phrase, again, appears to me some- 

 what difficult to understand ; but whatever its meaning, Prof. 

 Tyndall totally misrepresents what I have done. For more than 

 a year I was in possession of and had matured my ideas ere I put 

 pen to paper with a view to publication \ and when, in August 

 1863, I read my papers at the British Association, it was not 

 with a view of mounting any " high horse of Neptune," but 

 with a view to induce that body to help me to execute the expe- 

 riments I had proposed*. 



* The readers of the Philosophical Magazine who remember Prof. Tyn- 

 dall's recent diatribes against Mr. Joule, will but smile at the consistency 

 he exhibits in attempting to cry down at present the value of theoretical 

 speculations unsupported by experiment. 



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