696 
MR. W. CROOKES ON RADIANT MATTER SPECTROSCOPY. 
mere modification of the yttrium spectrum induced by the presence of some extra¬ 
neous body. We know that yttria per se has little or no phosphorescence (75), that 
this power chiefly resides in the ignited sulphate. Might it not happen that some 
other earth with molecules peculiarly sensitive to the longer vibrations would confer 
upon yttria some of its sensitiveness to the red end of the. spectrum ? 
It would be too much like a repetition of my paper on the yttrium spectrum quest 
were I to detail the numerous experiments and false starts with samarskite, orangite, 
thorite, strontianite, coelestine, perofskite, cerite, coral, &c. ; but I may be permitted 
to extract from an enormous mass of chronicles which must remain unpublished, some 
few experiments which will usefully emphasize what I may call the nodal points in 
this research. 
“ X” from Samarskite. 
101. It was to be expected that samarskite would contain x. It occurred, however, 
very little in the yttria group, but was found with the decipia residues (47, 49), or the 
earths forming, with potassium, insoluble double sulphates,—ceria, lanthana, didymia, 
decipia, samaria,, together with a little thoria and zirconia. These residues were 
dissolved in hydrochloric acid, precipitated with ammonia, washed till free from 
potassic salts, re-dissolved, and precipitated as oxalates. The filtrate was set aside in 
Winchester quart bottles, and after standing for some weeks a further quantity of 
insoluble oxalates was found deposited at the bottom of the bottles. These were 
collected, and appeared to be very rich in x; but on attempting to work them up 
vexatious anomalies constantly started up : suddenly the orange band would disappear, 
and after being lost sight of for a week or two, would return in a manner equally 
unaccountable ( 3, 99, 108, 115). 
Thorite and, Orangite. 
102. Early in my research thorite and orangite (26) had given a brilliant spectrum, 
afterwards identified with that of yttria (70). When hunting for x some of the 
insoluble double sulphates from these minerals (32) were treated like the samarskite 
double sulphates to remove potassium (101), and examined in the radiant matter tube. 
Here, also, was found the orange-band spectrum, quite different from the yttrium 
spectrum of the soluble sulphates; but, as usual, it behaved in a most capricious 
manner. 
Perofskite. 
103. An American friend, Mr. George F. Kunz, with great kindness sent me some 
pounds’ weight of the rare mineral perofskite (calcic titanate), in fine crystals, from 
Magnet Cove, Arkansas, together with a huge number of specimens of associated 
minerals from the same locality. The perofskite was found to be richer in x than any 
mineral yet examined. At great sacrifice of material a small portion of an earthy 
