150 Scientifie Intelligence. 
phate (which alone gives only a weak continuous spectrum) even 
in the proportion of only one per cent, the mixture fluoresces 
with a magnificent green color, reaching its maximum brillianey 
when five per cent of the oxide is present. Calcium carbonate, 
which does not fluoresce when not previously heated, and which 
fluoresces violet-blue after calcination, gives, on adding a trace of 
manganese, a magnificent orange-yellow color. Magnesium sul- 
phate alone, after heating to redness, fluoresces feebly greenish- 
white; but a trace of manganese causes it to fluoresce of a superb 
red color. Zine sulphate, calcined, fluoresces feebly pale rose 
color; but with manganese, it gives a splendid orange-red color. 
Cadmium sulphate, which alone gives a feeble ereenish- -yellow, 
gives with manganese a brilliant greenish- yellow color. Stron- 
tium sulphate, however, which fluoresces of a pale lilac color 
alone, has its color or intensity scarcely changed by the addition 
of manganese. Lead sulphate when alone gives a violet-blue 
feebly, which is changed by manganese to a beautiful yellow. 
Glucinum sulphate has the color of ‘its fluorescence changed from 
green to yellowish-green. In all these cases the spectrum is a 
broad band reaching from wave-length 672-619 to 480-456, hav- 
ing a maximum at 600 to 550. 
Bismuth sulphate, which alone does not fluoresce after calcina- 
tion, gives to calcium sulphate, even in very small proportion, the 
property of emitting a beautiful red-orange fluorescence. To 
strontium sulphate it gives a still more brilliant fluorescence, of a 
tint somewhat less red. To barium sulphate, which alone does 
not fluoresce, a trace of bismuth oxide gives a fine orange-red 
fluorescence. To magnesium sulphate, bismuth oxide gives a red 
fluorescence, still less orange. No result was obtaincd with zine, 
with cadmium or with lead sulphate. The spectrum bands extend 
over a considerable range in the spectrum and are characteristic. 
Purified yttrium sulphate, which alone gives only traces of the 
yellow band Za yields, when containing two per cent manganous 
sulphate, a fine yellow-green fluorescence whose spectrum consisis 
of a wide band beginning nebulously at wave-length 650, reaching 
a maximum at about 564, having an appreciable intensity at 509- 
504, and ending vaguely at 489-484. A similar mixture with 
bismuth sulphate gives a beautiful red fluorescence, resolved by 
‘the spectroscope into a band beginning nebulously at 684, reach- 
ing a Maximum at 642-640 and ending vaguely at 579- 577. On 
treating calcium sulphate with manganous and with bismuth sul- 
hates, with both of which it is active, the fluorescence was 
yellow at the center and pale green farther from the electrodes, 
The red-orange band was brighter than the green; but on heating 
the tube it almost disappeared. When cadmium sulphate was 
mixed with manganous and with bismuth sulphates, with the 
former of which only it fluoresces, the yellow-green light gave a 
spectrum somewhat more extended and less brilliant than that 
produced by manganese alone. When both zine and calcium 
sulphates were mixed with manganous sulphate, in various pro- 
