
Analysis of Bright Spectrum Lines. 503 
due to the mercury green radiation in the two cases, when 
the components were visible, as exemplified by the photograph 
given by Fabry and Perot, as referred to above, and when, with 
the same Eo aeitien of the silvered plates, the components were 
not present, as exemplified by fig. 13, Plate XX VI., the ques- 
tion arose—Has the change i in the conditions given birth to 
one or more satellites? The sharpness of the fringes in both 
cases, the unequal change in the intensity of the various com- 
ponents under variable conditions, as is shown when the 
eapillary of a vacuum-tube is heated, and in the fact that the 
results, given in the above table, upon the distances between 
the components are in poor agreement, which is probably due 
to the different circumstances surrounding the radiation, all 
point to the possibility of the production of satellites. It, 
must not be forgotten, however, that at the separation of the 
plates necessary to show the presence of the components the 
interference-bands are very close to one another, so that it is 
impossible in this method for an interference-fringe due to 
the birth of a satellite to appear without overlapping some 
part of the interference-fringes of the other components and 
hence producing a new ice of light in the interference 
pattern which would naturally lead to differ ent results. 
The investigations of the variations in the wave-length 
and intensity of radiations separated by the grating on 
account of variation in pressure, electrical condition of the 
discharge, and the chemical nature of the dielectric surround- 
ing the SEES substance, is at present a very fruitful field. 
For these changes in these widely-separated lines lend them- 
selves to measurement. It is hoped that a method will be 
found which will more readily show and give measurements 
of the many changes that occur in radiations whose wave- 
lengths, and hence their frequencies, do not differ greatly, so 
that ultimately some knowledge as to the mechanics ot the 
systems of moving electrons “constituting the atom whose 
periods differ by small eect to those obtainable 
at present—may be obtained. A step in this direction has 
been made by Lummer. The reproductions in the Ann. d. 
Phys. x. p. 473 (1903) show excellently the complicated 
structure of these bright radiations. The method proposed 
above, employing longer plates, is worthy of a fair trial. 
My heartiest thanks are due to the professors and lecturers 
in physics in this University, especially Professor Ames 
and Professor Wood, and also to my fellow students whose 
kind assistance in word and deed has greatly facilitated 
these experiments. 
Physical Laboratory, 
Johns Hopkins University. 
