382 Mr. J. S. Russell. The Wave of Translation. [June 16, 



merits only, made by use of a Leyden jar, that I believe to be 

 decisive, and to prove irrefutably that Swan's spectrum cannot be 

 ascribed solely to hydrocarbon. As to the phenomenon shown by 

 sparks, it is not quite so convincing; for, accepting Wiillner's* 

 ideas, one could object that the spark affecting only a set of molecules 

 of infinitely small transverse section could have carried forth from the 

 electrodes an exceedingly small quantity of hydrogen, which would 

 quite escape observation when expanded throughout the whole vacuum 

 tube, but would be sufficient to induce the hydrocarbon spectrum in 

 the line of the spark. This explanation, however, I do not think to be 

 at all probable. The tube used in these experiments was of common 

 size ; the ends of the electrodes, which were of aluminium, had a dis- 

 tance of about 15 centims. from one another. Some results, differing 

 from those just mentioned, were obtained in a wide spectrum tube 

 without capillary tube, the ends of its electrodes being distant about 

 3 centims. from one another. The spark then no longer exhibited 

 Swan's spectrum, even when the carbonic acid was not dried with 

 the utmost care, as in the above-mentioned researches ; but there 

 were seen the enlarged maxima of Watts' second spectrum, which I have 

 shown by some researches, of which a short account has been published 

 in the "Berlin. Monatsb.," 1880, p. 791, to be generally due to the 

 continuous form of discharge, according to the nomenclature of Messrs. 

 Thalen and Angstrom. If the density of the gas was still increased, 

 there flashed a very brilliant line spectrum, never before observed by 

 me, in a tube of common size. These facts, at all events, show that 

 there exists some relation between the different orders and forms of 

 spectra and the conditions of discharges (probably, according to my 

 opinion, the quantities of electricity sent through the unit of space in 

 the unit of time, till now unknown to us) that will doubtless become 

 clear as soon as the causes governing spark discharges shall be better 

 recognised — a subject on which Sir W. Thomsonfv says that it is 

 difficult even to conjecture an explanation. 



V. " The Wave of Translation and the Work it does as the 

 Carrier Wave of Sound." By John Scott Russell, F.R.S. 

 Received June 13, 1881. 



Synopsis. 



Short history of the wave of translation discovered by me in 1832-3. 

 Investigation of its shape, nature, speed, and difference from all other 

 waves in its character as a solitary carrier wave. 



* Wiillner, " Lehrbuch der Experimental Physik," vol. 2, p. 250, &c. 

 f Papers on " Electrostatics," &c, p. 247. 



