434 C. PIAZZI SMYTH ON MICROMETRICAL MEASURES OF 



spectrum than any of the London gentlemen, — and yet, with myself, was pushed 

 out of the pale of recognition through all that long period from 1862 to 1875 

 But. what occurred in that latter year % 



In 1875 was published the grand Memoir of MM. Angstrom and Thalen, 

 wherein a very polite denial is given to the correctness of one of the most 

 important of Dr Attfield's assertions, viz., that the candle-spectrum was an 

 invariable accompaniment of a CO flame burning in the open air.""' 



Imperfect methods of preparing CO (Carbonic Oxide), argued M. Thalen, 

 may easily allow CH gas to be present and give its spectrum ; — but pure CO 

 does not give it. So also I have found with my tube experiments, — for while 

 some of M. Demichel's very carefully prepared tubes of CO did not reveal a 

 particle of any of the bands of the CH Blow-pipe flame, — certain other 

 examples of CO by a London maker exhibited so much of the said bands, not 

 too as a mere residual accidental impurity in the tubes, but as a something 

 introduced pari jiclssu by an erroneous chemistry in making the gas, for it 

 inweased always with the 'pressure, that I wrote at last for the particulars of 

 the manufacture; and then discovered that the maker had been using a very 

 weak and watery example of mere commercial Sulphuric Acid, instead of the 

 most pure and anhydrous example that could be obtained. 



The outcome therefore in 1875 of the opinions of such men as Angstrom 

 and Thalen, could not be altogether repressed and repudiated even by the Royal 

 Society, London. But that Society has since then had a severer trial to bear ; 

 for almost in the et tu Brute manner of the stricken Caesar, they have had to 

 read the later essays of Professors Liveing and Dewar, from the Cavendish 

 Laboratory at Cambridge ; and find therefrom, that those distinguished 

 scientists have come to precisely MM. Angstrom and Thalen's conclusion; 

 viz., that the Candle-spectrum is a CH, not a C, spectrum ; and that its 

 uniformity through all varieties of CH chemicals, depends upon the formation 

 of Acetylene, C 2 H 2 , in the course of the combustion or incandescence. 



In short, the mental confusion that has now overtaken those who have 

 ruled the London world of spectroscopy in this matter, so long, — is illustrated 

 at the end of the British Association's Report upon it ; — for it terminates with a 

 disjointed, unnecessary and primitively simple statement of the spectrum places 

 of the mere general beginning of the Orange, the Citron, and the Green bands 

 of what may now be firmly called by every one, the CH spectrum. 



Unnecessary was that proceeding of the Committee, because all men have 



* From p. 14 of Messrs Angstrom and Thalen's Memoir. "Quant a l'observation de M. 

 Atteield que l'oxyde de carbone donne le spectre ordinaire des carbures d'hydrogene, nous devons 

 remarquer que cela no s'accorde pas bien avec nos proprcs experiences. 



" I >ans un tube de Geissler, contcnant de l'oxyde de carbone ou de l'acide carbonique, on peufc 

 certainemeut trouver des traces des spectres des carbures d'hydrogene, puisque le gas n'est jamais 

 parfaitement sec." 



