SIR W. CROOKES ON THE PHOTOGRAPHIC SPECTRA OF METEORITES. 
416 
record the outcome of a research which, although not giving the expected result, 
furnishes information that may be valuable. 
In connection with the several theories as to the origin of Meteorites it was thought 
that a thorough examination of the occluded gases might possibly reveal the presence 
of some of the inert gases, or of those hypothetical elements thought to be present 
in some of the hotter stars. At the present time the manipulation and spectroscopic 
investigations of gases have reached a high state of development, and a far more 
thorough investigation of the subject is possible than was the case years ago when 
much work was done by Prof. A. W. Wright, of Yale College.* 
It is now possible and comparatively easy to separate from the gaseous mixture 
liberated by heating the meteorite, the hydrogen, oxygen, carbon compounds, &c., 
whose presence is not indigenous, and to reveal any of the non-valent elements that 
may be present. One of the most popular methods is to employ the process of 
absorption by charcoal at low temperatures—the same method that has been 
employed with so much success upon the gases contained in spring waters, &c. 
There are, however, certain experimental and manipulative difficulties that I wished 
to avoid. 
Some years ago Frederick Soddy, Esq., F.B.S., published an account of a device 
in which the absorption by metallic calcium at its volatilisation temperature was 
made to answer the same purpose.'!' 
Soddy’s vacuum furnace, although a very ingenious piece of apparatus, is too 
elaborate for my purpose—so while adopting the principle I have modified the 
details. 
The calcium cut into small fragments is placed in a small vessel of iron open at one 
end like a miniature test-tube and introduced into a similar but larger tube of fused 
quartz ; it is then only necessary to attach the quartz tube to the pump and gas 
apparatus, and by applying a Meker burner so as to heat it to full redness the 
volatilisation of the calcium and subsequent absorption of the chemically valent gases 
are entirely under control. 
By this means the gases—obtained by heating to redness each of the aerolites—- 
were examined spectroscopically at different pressures. Fig. 4 gives an outline of the 
apparatus actually used. A special and simple form of Sprengel pump was made as 
shown, so that if needful it could be replaced by a new one for each meteorite. A is 
the vacuum tube ; B the quartz tube with the iron vessel containing lumps of clean 
metallic calcium ; C, a tube of hard glass, with the powdered aerolite ; D, phosphoric 
acid to absorb moisture ; E, an inverted tube filled with mercury in which any gas 
not used could be collected. 
The procedure was to exhaust thoroughly, and well spark the vacuum tube so as 
to expel any gas occluded in the electrodes, and continue the exhaustion until the 
* ‘American Journal of Science and Arts,’ 3rd series, 1876, p. 253. 
f ‘Proceedings of the Royal Society,’ vol. 78, series A, 1907. 
