QO 
R ] THE GEELONG NATURALIST. 
to vibrations of different velocities, the slowest being those pro- 
ducing red, and the quickest those of violet, the other colors 
being in between. It is found that the incandescent vapors of 
the various elements produce when the light is passed through 
a prism different colors, being fixed and definite of any given 
one. For instance, incandescent sodium vapour gives bright 
yellow lines, lithium gives a red line and an orange one, while 
hydrogen produces one red, one greenish blue, and one violet line. 
Again, if pure white light, such as the electric light or the lime 
light, be passed on to the spectrum, we get a continuous band of 
light of the successive colops, red, orange yellow, green, blue, 
indigo, and violet. If now the white light is made to pass 
on its way to the spectrum through an atmosphere of the incan- 
descent vapor of an element, a dark line or lines will appear on 
the spectrum, at the part which corresponds to the bright line 
or lines which are given by that element when separately 
examined. It is this fact that enables us to find what elements 
exist in the heavenly bodies. Thus, if we pass the light from 
the sun on to the screen, we find a great number of dark lines, 
so that the spectrum is broken and not continuous. Thus in 
the yellow part are found a couple of dark lines, corresponding 
to the bright lines given out by sodium. Hence we conclude 
that there must be sodium in the sun. Similarly we conclude 
that iron, hydrogen, copper, zinc, and various other elements are 
present in the sun. Some of the dark lines of the solar 
spectrum, however, correspond to rays which have been absorbed 
by our own atmosphere, for their appearance changes with the 
position of the sun being darkest at sunrise and sunset, when 
the rays pass through the greatest breadth of the atmosphere. 
During a total eclipse of the sun, rose-colored flames appear to 
stand out from various parts of the boundary of the sun's disc. 
These flames are shown by the spectrum to consist of 
incandescent hydrogen. In the same way, by analysing the 
light from the fixed stars, the presence of various elements may 
be inferred. In order to effect this spectrum analysis, an 
instrument called the Spectroscope is used. A full description 
of this instrument was then given, and its use illastrated by 
some experiments with the Spectroscope belonging to the College 
Physics Class. Amongst the many uses of the Spectroscope are 
the measurement of the motion of the so-called “fixed " stars, 
and the explanation of spots on the sun. 
Those members of the Club who may wish. to follow up the 
subject may obtain the very latest facts and figures concerning 
spectroscopic research in the address of the President of the 
British Association, Dr. Huggins, delivered in August last, a full 
report of which can be found in the London Times of August 
90th, 1891. 
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