MR. W. CROOKES ON RADIANT MATTER SPECTROSCOPY. 
697 
body was obtained giving the orange-band spectrum more brilliantly than I ever had 
seen it before. Analysis failed to detect anything in it but lime (5,9), the flame 
spectrum showed lime, and the atomic weight came out RO = 55‘3, CaO being 56. 
Calcite. 
104. Mr. Lettsom, understanding I was engaged in quest of an unknown body 
supposed to be associated with calcium, most kindly sent me specimens of rare and 
curious minerals; and through his good offices Professor Albin Weisbacti presented 
me with an extensive set of balcites ; these, prior to the invention of the spectroscope, 
had been measured by Professor A. Breithaupt, who, owing to the discordant 
measurements, held what is known as “ calcium ” to consist of two or more allied 
elements, which as yet chemists were unable to separate. 
These calcites were treated as usual and examined most carefully in the radiant 
matter tube. In one of them only was a trace of yttria found, but the orange-band 
spectrum was very faintly seen in six of the thirteen specimens. The others shone 
with the usual greenish-blue phosphorescence of calcic sulphate, giving no lines or 
bands in the spectrum. 
I am also indebted to Mr. Lettsom for a specimen of calcite from Branchville, S. 
Carolina, which, when heated, has the curious property of glowing strongly with a 
golden-yellow light showing a faint continuous spectrum. In the radiant matter tube 
the phosphorescence was very brilliant, but there was no discontinuity in the spectrum, 
only a concentration of light in the red portion. 
Dolomite. 
105. Another curious mineral, for which I am also indebted to Mr. Lettsom, is a 
granular dolomite from Utah. When scratched with a knife or struck with a pick it 
emits so strong a phosphorescent red light that the miners call it Hell-fire Rock. 
By itself in the radiant matter tube it brightly phosphoresces with a reddish light, 
showing no bands, but a concentration of light in the red. Treated with sulphuric 
acid in the usual manner, and then examined in a, vacuum tube, a similar continuous 
spectrum was observed. Chemical analysis showed that it was a nearly pure double 
calcic and magnesic carbonate, with a little iron, alumina, and phosphoric acid. 
Amongst other minerals found to give the orange band spectrum I may mention 
zircon, euxenite, tyrite, fergusonite, rhabdophane, cerussite, apatite, galliferous 
blende, argentiferous galena, anglesite, harmotome, allanite, cerite, magnesite, oolite 
from Bath, &c. 
Coral . 
106. In my former paper (88) I mentioned that a specimen of pink coral contained 
about a half per cent, of yttria, judging from the very strong yttrium spectrum it 
