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XIX. On the Action of Rays of high Ref Tangibility upon Gaseous Matter. 
Ry John Tyndall, LL.D., F.R.S. 
Received December 4, 1869, — Read January 27, 1870. 
§ 1 - 
Introduction. 
W ithin the last ten years I have had the honour of submitting to the Royal Society a 
series of investigations the principal aim of which was to render the less refrangible 
rays of the spectrum interpreters and expositors of the molecular condition of matter. 
Unlike the beautiful researches of Melloni and Knoblauch, these inquiries made 
radiant heat a means to an end. My thoughts were fixed on it in relation to the matter 
through which it passed. Placing before my mind such images of molecules and their 
constituents as modern science justifies or renders probable, such images of the lumini- 
ferous ether and its motions as the undulatory theory enables us to form, I endeavoured 
to fashion and execute experiments founded upon these conceptions which should give us 
a surer hold upon molecular constitution. 
Thus, definite physical ideas have accompanied and guided the whole course of these 
researches. That matter is constituted of atoms and molecules has been accepted as a 
verity throughout. The phenomena under examination rendered it impossible for me 
to halt at the law of multiple proportions, which so many chemists of the present day 
appear inclined to make their intellectual bourne. In following up a train of ether 
waves, in idea, to their source, I could not place at that source a multiple proportion ; 
the waves could not be connected physically with such a multiple ; I was forced to put 
there a bit of matter, in other words, a molecule , which bore the same relation to the 
ether as a vibrating string does to the air which accepts its motions and transmits them 
as waves of sound. 
One result among many others which these researches established will, I think, play 
an important part in the chemistry of the future. I refer to the proved change of rela- 
tion between the luminiferous ether and ordinary matter which accompanies the act of 
chemical combination. Here, without any alteration in the quantity, or in the ultimate 
quality of the medium traversed by the ethereal waves, vast changes may occur in the 
amount of wave-motion intercepted. Let pure nitrogen and ordinary oxygen be mixed 
mechanically together in the proportion by weight of 14 : 8. Radiant heat, it is now 
known, will pass through the mixture as through a vacuum. No doubt a certain amount 
of heat is intercepted ; but it is so small an amount as to be practically insensible. At 
all events it is multiplied by hundreds, if not by thousands, the moment the oxygen and 
nitrogen combine to form nitrous oxide. Or let nitrogen and hydrogen be mixed me- 
MDCCCLXX. 2 Y 
