ME. J. N. LOCKYEE ON SPECTEOSOOPIC OJBSEEVATIONS OF THE SUN. 
433 
line. In resuming the subject, we pointed out the existence of a new hydrogen-spectrum, 
corresponding to a lower temperature, but having no resemblance at all to the spectra 
of the first order of nitrogen, sulphur, &c. In this spectrum, of a peculiar character, if 
fully developed, we observe a great number of well-defined bright lines, almost too nu- 
merous to count and represent by an engraving, but brilliant enough to be examined 
with a magnifying-power of 72, after the light has passed through four prisms. 
“ On sending the direct discharge of Ruhmkorff’s coil through a tube of glass from 
one-fourth to one-eighth of an inch in diameter, provided with electrodes of platinum or 
of aluminium, enclosing hydrogen at a tension of 5 to 10 miliims., a luminous thread of 
light of a bluish-white colour was seen passing along the axis of the tube, without 
touching the glass. When analyzed by the prism, it gave a faint spectrum of the above- 
mentioned numerous bright lines, especially within the red and the yellow. Among 
these lines neither Ha nor Hy were seen ; H/3 only appeared, but less bright than many 
other lines. By interposing the Leyden jar and gradually increasing its charge, all the 
lines became brighter, H/3 surpassing all other lines in brilliancy; Ha appeared 
beautifully, Hy fainter. Hence we conclude that the numerous bright lines belong 
neither to the vaporized metal of the electrodes, nor to the decomposed interior surface 
of the glass, but solely to the hydrogen, constituting a new spectrum of it. This spec- 
trum may be seen simultaneously with the three characteristic lines Ha, H/3, Hy; 
but at an increased temperature, when these lines begin to expand, it entirely dis- 
appears.” 
MM. Plucker and Hittorf also determined the action of the discharge of a small in- 
duction-coil through a tube enclosing hydrogen which was gradually rarefied to the 
highest tenuity to be reached by a Geissler’s exhauster ; they found that, as the exhaus- 
tion proceeded, the red colour of the gas gradually faded into an “undetermined violet,” 
and that Ha disappeared, while H/3, though fainter, remained well defined. 
With hydrogen gas in Geissler’s tubes, then, the following facts are established: — 
I. With a certain degree of rarefaction and temperature, we obtain three character- 
istic lines, Ha, H/3, and Hy. 
II. By increasing the temperature, we expand Hy first towards both ends of the spec- 
trum, then H/3, Ha remaining almost unchanged after Hy has passed into an undeter- 
mined large violet band. 
III. By increasing the tenuity, Ha disappears first, H/3 remaining w 7 ell defined, and 
moreover the colour of the ignited gas changes to the eye. 
IV. Under certain conditions, which are not stated in the memoir, new lines appear 
in the spectrum, especially in the neighbourhood of the sodium-line. 
Assuming that hydrogen gas is present in the chromosphere and prominences, we 
have the following facts to place side by side with those just stated : — 
I. In place of the three lines we have but Ha and H/3. 
II. H/3 is in process of expansion, the expansion increasing as the sun is approached, 
and Hy is so far expanded that it no longer exists as a line ; most careful observations 
mdccclxix. 3 M 
