24 Mr. EL Eamage. Relations of Spectra, Densities, [Nov. 7, 



A supposition such as the above would imply that one molecule can 

 produce only one line at a time. Lord Kayleigh* has already made a 

 suggestion of this nature in discussing a formula deduced theoretically. 

 He wrote : — " In this case instead of supposing that the whole series 

 of lines correspond to various modes of one highly compound system, 

 we attribute each line to a different system vibrating in a special 

 mode." 



The data available at present are far from complete, and some of the 

 suppositions are open to question. For instance, the value of N is 

 adopted from the formula for hydrogen, without considering the 

 influence of its atomic mass. Although the effect of this mass may be 

 small, it may be sufficiently great to complicate the results calculated 

 from it, so as to obscure a regular order in the changes produced by 

 the increase in the masses of the elementary substances. 



An article by Professor Pickering t on " The Spectrum of f Puppis," 

 contains statements which confirm the views expressed above regarding 

 the formula of Kayser and Eunge. He has found that a slight modifica- 

 tion of Balmer's formula 3636-1 ( 2 n Y gave the lines of the ordinary 

 series of hydrogen and the additional series more accurately than 



Kayser's formula, 1 = A + B — + C — - . He remarked: " On the 



A m 2 nr 



whole, the observed values agree more nearly with the first formula 

 than with the second. This is remarkable, if it does not represent the 

 true law, since this formula contains no arbitrary constants." 



A Comparative Study of the Densities and Melting Points of some Groups 



of the Elements. 



The graphical method, employed in the investigation of spectra, has 

 been extended to two other properties of the elements — density and 

 melting point. These properties were chosen because the data con- 

 cerning them were more complete than the data relating to other 

 properties. 



It is hoped that the graphical method of investigation may, as time 

 and data permit, be extended to the other properties of the elements. 

 We have observed that the shift of some of the lines in spectra is 

 proportional to the atomic mass ; of others, to the square of the atomic 

 mass. The proposed extension of the work will tell us which pro- 

 perties of the elements follow the first order, which follow the second, 

 and possibly of some which vary with some other power or function of 

 the atomic mass. Such information will doubtless throw considerable 



* ' Phil. Mag.,' vol. 44, p. 361, 1897. 



t ' Astrophys. Jour.,' April, 1901, p. 232. 



