108 Mr. L. Schwendler on the General Theory 



nished room — under these conditions only did I carry out my 

 research on the spectrum of carbon. The absence of Plates and 

 measurements in my paper is not ". . . . explained (in a memoir 

 crowned by being printed in the Philosophical Transactions of the 

 Royal Society of London) by its one chief burden (viz. putting 

 pure carbon vapour for hydrocarbon) having been grateful to 

 the then already formed prejudices of the secret committee who 

 passed it," but by the fact stated in my paper, that Professor 

 Swan had already measured and recorded, confessedly with great 

 accuracy, the position of the lines of the spectrum (observed by 

 him in hydrocarbon flames*). 



Spectral analysis brings to light marvellously minute traces of 

 matter, traces difficult to remove even from the surfaces of ap- 

 paratus, and still more difficult to extract from large volumes of 

 other matter. Have I overlooked traces of hydrocarbons in some 

 of my flames and tubes ? Scarcely ; for I adopted all precau- 

 tions known to chemists to obtain chemical purity and cleanli- 

 ness. Again, other chemists, armed with prejudice against my 

 conclusions, have ended by confirming those conclusions. Still 

 here perhaps is room for sound original investigation ; something 

 new could hardly fail to be discovered by eyes trained to observe. 

 Is it too much to expect that a gentleman occupying so high a 

 position as Mr. Piazzi Smyth will either support his statements 

 by such sound evidence or withdraw them altogether f ? 



John Atteield. 



XV. On the General Theory of Duplex Telegraphy. 



By Louis SchwendlerJ. 



[Continued from vol. xlviii. p. 138.] 



THE first part of this investigation concluded by giving 

 (Phil. Mag. vol. xlviii. p. 138) the best relations between 



* Had so good an observer as Swan worked, instead of the writer, in 

 1862, with the light just then shed on spectroscopy, I am sure he would 

 have looked for the spectrum in flames not containing hydrogen, and would 

 thus have discovered what I discoved, the spectrum of carbon. — J. A. 



t The tone of Mr. Piazzi Smyth's communication renders desirable on 

 my part an expression of regret that my duties in the department of che- 

 mistry to which I was appointed within a month of the publication of my 

 research on the spectrum of carbon, have quite prevented me from carrying 

 on similar researches. That regret is much tempered, however, by my 

 belief that such work would have been done far less efficiently by me than 

 by men like Pliicker, Morren, Lielegg, Troost and Hautefeuille, and Mar- 

 shall Watts. I am obliged to add that nevertheless my labours, from the 

 promotion of original investigation in other directions, have neither been 

 few nor unsuccessful. This is the only notice I can take of the personali- 

 ties in Mr. Piazzi Smyth's paper. — J. A. 



X From the Journal of the Asiatic Society of Bengal, vol. xliii. part 2, 

 1874 (read on the 4th of February, 1874). Communicated by the Author. 



