700 
MR, W. CROOKES ON RADIANT MATTER SPECTROSCOPE. 
Every conceivable mixture was now made of lime with other bodies, but whilst I 
frequently obtained faint indications of orange band there was never sufficient to 
satisfy me that I had artificially formed the spectrum-bearing body; the traces 
observed were evidently due to the all pervading presence of the sought for body. 
So far all had been contradictory and disheartening. Analogy with the yttrium 
results failed to throw light to guide through the gloom. The hypothesis that the 
body sought was an earth, widely diffused in minute quantities only, and that its 
anhydrous sulphate gave a phosphorescent spectrum in the radiant matter tube, had 
guided me a certain distance and then led me widely astray. A new factor must now 
be taken into account—the presence of a calcium compound appeared to be necessary. 
An earthy body which, when treated and tested in the usual manner, fails to show 
the faintest glow of an orange-band spectrum, can by admixture with calcic sulphate 
be made to yield a pure and brilliant spectrum, rivalling in clearness and beauty that 
given by yttric sulphate. 
111. Of the two components of the phosphorescing body—calcium and x —which is 
the necessary and which is the variable factor ? 
This question did not appear difficult to answer. In the first case the calcium must 
be kept the constant, and x be made the variable quantity. 
A piece of pure colourless Iceland spar—the sulphate from which had been proved 
to phosphoresce normally with a greenish-blue light, without bands or concentration 
in any part of the spectrum (164)—was dissolved in hydrochloric acid, and mixed 
with about 10 per cent, of various metallic sulphates. Sulphuric acid was added, the 
mixture evaporated to dryness, ignited, and tested in a radiant matter tube. The 
bodies thus used to replace x, in addition to the more common earths, were the earths 
from samarskite—enumerated in the first part of this paper (40)—in as pure a state 
as I could get them, together with various earthy precipitates, oxalates, kc., obtained 
from different minerals during the preceding operations. 
These experiments resulted in an embarras cle richesse. Whereas, hitherto, I had 
considered the orange-band-forming body rare and sparsely distributed I now found it 
sharing with yttrium the attribute of ubiquity. The answer to my question was too 
full, and left me again in doubt as to whether calcium or x was the variable quantity. 
The yttrium spectrum turned up in this series of experiments about as frequently 
as the orange-band spectrum. I knew that in such cases yttrium was present as an 
impurity; might it not be that the almost universal occurrence of the orange-band 
spectrum was equally caused by a minute but varying quantity of x in the earths 
under test ? 
112. I took them one by one and submitted them to further severe chemical treat¬ 
ment, fractionally precipitating them, in cold dilute solution, with weak ammonia, or 
fractionally crystallising their oxalates from nitric acid. As the purification progressed 
the orange-band spectrum generally lessened in intensity till in the case of many 
earths it faded out altogether, and in most of them it gave evident indications of 
