AFTER INSOLATION. 13 
submitted to many and varied experiments. It is 
best obtained by the calcination of pulverized 
. sulphate of baryta, made into a firm paste with 
common gum. It should be preserved in a bottle 
which closes hermetically with a glass stopper. 
When such a bottle and its contents are ex- 
posed to the rays of the sun, or even to daylight, 
for a certain time, and then taken into a dark 
room, the sulphuret of barium is seen to be beau- 
tifully phosphorescent, or to shine like common 
phosphorus, and the phenomenon will sometimes 
last a whole hour. The most intense cold does not 
affect this phosphorescence, and it manifests itself 
precisely in the same manner whether the sulphuret 
be placed im vacuo or in the air. 
When nitrate of lime is melted for ten minutes 
in a crucible, it leaves a residue which manifests, 
to a less extent, the same phosphorescent property. 
This residue, which is nothing more than pure 
lime, or a mixture of lime and nitrite of lime, was 
known for some time as “ Baudowin’s phosphorus.” 
A like phenomenon is observed with calcined 
shells. 
Sulphuret of calcium possesses the same phos- 
phorescent qualities as the sulphuret of barium 
alluded to above; hence the former is sometimes 
known as “ Oanton’s phosphorus.’ Canton pre- 
pared it by heating a mixture of three parts of 
sifted calcined oyster-shells, with one part of sul- 
