TROWBRIDGE. — HIGH ELECTROMOTIVE FORCE. 2< 
contain. Hydrogen may be present, but it is concealed. Oxv ; n shows in presence 
js; the constituents of rarefied air are undoubtedly al\va\ 
luW 
only by probable oxides; the constituents 
there. The conditions which prevail in the case of discharg 
ries seem to be analogous to those in the case of discharges under liquids. In this 
latter case we also have reversals of metallic lines; and, moreover, certain character 
istic lines of metals are wanting. See "Spectra from the Wehnelt Interrupter." Harry 
W. Morse, Proceedings American Academy of Sciences, May, 1904. 
These results make one doubtful in regard to ihe entire subject of spark pectrt 
which are observed between metallic terminals in ordinary air; and we are forced to 
ask, what influence does the environment have upon the character of these spectra, — 
to what must we attribute the absence of oxygen lines? And even if we take -park 
spectra between metallic terminals in an atmosphere of hydrogen or nitrogen, we ar< 
not sure that the results are not modified by the gases which are occluded in the 
metallic terminals. 
Are we sure that, even in electrodeless tubes, helium is a product of disintegration 
of radium 
peak, and is not a result of 
in the environment of glass or quartz, — a stimulus which may bring to light 
helium which has refused to manifest itself by chemical anal) 
,'c? 
In general it may be said that the conductibility of the volatilization product- 
either from the walls of the tubes or from the metallic terminals, determine the occur- 
rence of the spectral lines or bands. The spectrum, for instance, of silica completely 
masks the spectrum of the iron terminals when the latter are placed not more than 
five millimeters apart. When the terminals are of different metals, the spectrum of 
the more volatilizable metal predominates; or, more strictly, the spectrum of the better 
conducting vapor. 
Another striking fact brought to light by such discharge* in capillaries is the 
reversal of many of the spectral lines on broad hands. The broadening of the lines 
of the metals is generally toward the red end of the spectrum. The quantity of th< 
discharge appears to be the important factor in determining the character of the 
spectra ; electromotive force, per te, does not give new lines which can be detected by 
photography. The effect of high electromotive force begins to be evident at h 
exhaustions, and then only in producing cathode and X rays. 
This latter fact can be well shown by a Tesla coil, actuated by a Cooper-Ilewi 
mercury interrupter, such as was employed by Dr. G. W. Pierce, Proc. Amer. Acad 
1904. With a suitable step-up transformer, in connc tion with such an interrupter, I 
have studied the spectrum of hydrogen, and have not obtained a spectrum w 
r 
? 
