FORMING THE LOW TEMPERATURE SPECTRUM OF OXYGEN. 423 
with any very certain result ; for there are so many of such lines, unclaimed 
for any element, strewed all along the solar spectrum. But now that I had 
found four out of five lines to be triplets of an accurate kind, could anything 
further in the way of identification be ascertained ? 
In apparently the very place of the three fainter of the above-described 
triplets there is a close double of peculiarly thin Fraunhofer lines depicted by 
Professor ANGsTROM in his normal solar spectrum map; and in the place of 
the brightest of them, viz., ScHUSTER’s orange line, there is a triple* of the same 
kind of wtra thin lines; and not one member of all those four groups has 
been claimed for any known element by the great Swedish physicist. Yet I 
am by no means satisfied that the degree of correspondence is conclusive ; and 
can only hope that those who have the means will positively confront the new 
oxygen triples with the sun itself, and inform us what they find. 
Oxygen of the Earth’s Atmosphere in the Tellurie Solar Spectrum. 
If the long silence of the spectroscope touching oxygen in the sun was a 
wonder, and perhaps something the reverse of praise to those who used the 
supposed all-powerful instrument, what shall be said for its continued silence 
as to the presence of any free oxygen in the earth’s atmosphere, when some 
gases that are therein do make themselves most signally conspicuous on the 
solar spectrum, in the shape of dark lines or bands, growing as the sun 
descends in altitude, until they become at last more grandly thick and black 
than all the truly solar markings put together. 
_ Amongst these gigantic cases of Fraunhofer lines of some kind of telluric 
gaseous origin, we do indeed know, by a sort of inductive process rather than 
by any positive proof, that the band too hastily called “little a” and other 
bands and lines near C, and near D, are the spectroscopic proofs of watery 
vapour, as an invisible but potent gas in our atmosphere. But what makes 
the far greater A, or great B, and the a (alpha) band, no one pretends to know. 
At first sight it might well be suggested that they must be formed by one 
or other or both of the two grand constituents of the earth’s atmosphere as 
established by the chemists, viz., oxygen and nitrogen. But there we are 
instantly met by ANGsTROm’s inflexible law, promulgated by him in 1853, and 
repeated at page 39 of the description of his Normal Solar Spectrum in 1868 ; 
viz , that “‘a gas in the state of incandescence emits luminous rays of the same 
refrangibility as those which it can absorb.” Or, conversely, when it acts by 
* That triplicity is indeed there broken in upon by a far stronger line, which AN@sTROM traces to 
sodium, (Na); but such cases of mere optical juwata-position are frequent in the crowds of lines in 
much of the solar spectrum, without any physical connection being supposed to be implied thereby. 
