BY CLEAVAGE, ETC. 29 
In 1858, M. Landerer, of Athens, discovered 
that an organic salt, Valerate of quinine, becomes 
phosphorescent whilst it is being powdered in a 
mortar. The light emitted, which is very strong at 
first, becomes feeble as the pulverization proceeds, 
and ceases altogether when the crystals are reduced 
to powder. When the crystallization of fluoride of 
sodium takes place in a dark room, this salt is 
seen to twinkle with phosphorescent light. The 
same is observed when sulphate of soda and sul- 
phate of potash crystallize together. Waechter 
has observed that chlorate of baryta crystallizes 
from its solution in long rhombic prisms with pro- 
duction of leht. 
A most interesting production of light was ob- 
served and published (‘ Journ. des Sc. Physiques 
et Chimiques,’ de M. de Fontenelle), by Professor 
Pontus, in 1833, who showed that a vivid spark 
4s produced when water is made to freeze rapidly. 
A small glass globe, terminating im a short tube, 
is filled with water, the whole is covered with a 
sponge or cotton-wool imbibed with ether, and 
placed in an air-pump. As soon as the experi- 
menter begins to produce a vacuum, the ether 
evaporates, and the sponge or cotton-wool dries, 
the temperature of the water descends rapidly. 
But some instants before congelation takes place, 
a brilliant spark, perfectly visible in the daytime, 
is suddenly shot out of the little tube that termi- 
