[ 201 ] 



xxiy. 



ON THE CAUSE OF DOUBLE LINES AND OP EQUIDISTANT 

 SATELLITES IN THE SPECTRA OF GASES. By G. 

 JOHNSTONE STONEY, M.A., D.Sc, F.R.S. ; Vice-President, 

 Eoyal Dublin Society. 



{Abstract of a Paper read March 26 and May 22, 1891, and published in extenso in the 

 Scientific Transactions of the Eoyal Dublin Society, Vol. IV., Partxi., 

 p. 563). 



The gaseous spectra of the light monad elements, Li, Na, K, 

 Eib, Cs, are found to consist of three series of double lines. The 

 spectrum of hydrogen consists of one such series, and the spectra of 

 the heavy monads seem also to consist of double lines. Series of 

 double lines also present themselves in the spectra of elements of 

 higher atomicity, but are in them associated with more complex 

 groups. 



These double lines are due to events going on within the 

 molecules of the vapour ; and the aim of the communication of 

 which this is an abstract is to ascertain what these events are. It 

 is shown that each series of lines is due to the motion of an electron 

 — a fixed electric charge — within each molecule, or, at all events, 

 to some event which follows the same mathematical laws. The 

 motion may be represented by the equations — 



% = F,{t), 



which can be resolved by Fourier's Theorem into one definite series 

 of elliptic partials in each of which the electron is to be conceived 

 of as moving, the superposition of these motions being the actual 

 motion of the electron. These partials may lie in the same or in 

 different planes, and each of them has the form — 



X = a cos {6i), 

 y = h cos (0;!), 



a, 6, and being constants that vary from one partial to another. 



