﻿Interrupted Spectra of Gases. 



295 



^=1-000 2845, 

 /* F = 1-000 2820, 

 ^ G == 1-000 2791. 



Multiplying the foregoing wave-lengths by these values, we find 

 for the wave-lengths in vacuo, 



h =4102-37 tenth-metres, 

 F =4862-11 

 C = 6563-93 



which are the 32nd, 27th, and 20th harmonics of a fundamental 

 vibration whose wave-length in vacuo is 



0-13127714 of a millimetre, 



as appears from the following Table : — 



Observed wave-lengths 



reduced to wave-lengths 



in vacuo. 



Calculated values. 



Differences. 



Xth-metres. 

 h =4102 37 



F =4862 11 



C =6563-93 



Xth-metres. 

 ^X 131277-14= 4102-41 



5 yx 131277-14 =4862 12 



5 VX 131277-14 = 6563-86 



Xth-metres. 

 +0-04 



+001 



-007 



Thus the outstanding differences are all fractions of an eleventh- 

 metre, an eleventh-metre being the limit within which Angstrom 

 thinks that his measures may be depended on. 



The wave-length 0-13127714 of a millimetre corresponds to 

 the periodic time 4*4 fourteenth-seconds, if we assume the velo- 

 city of light to be 298,000,000 metres per second. 



Hence we may conclude, with a good deal of confidence, that 

 4*4 XlVth- seconds is very nearly the periodic time of one of the 

 motions within the molecules of hydrogen. 



The other harmonics of this fundamental motion in the mo- 

 lecules of hydrogen, viz. the 19th, 21st, 22nd, &c. harmonics, 

 are not found in this spectrum of hydrogen. But two other 

 spectra of hydrogen are known to exist in which there are a 

 great number of lines ; and possibly the missing harmonics will 

 be found amongst them when their positions shall have been 

 sufficiently accurately mapped down. A far more moderate de- 

 gree of accuracy will suffice in this case than was required by the 

 foregoing investigation. 



But it is from the examination of spectra of the Eirst Order that 

 the most copious results may be expected. These spectra con- 

 sist of lines ruled close to one another, and presenting in the ag- 



X2 



