PHOSPHORESCENCE. 3 3 I 



are exposed to the fumes of hydrochloric acid, they become, in six hours' 

 time, a beautiful red colour, which they preserve when placed in a dry, shady 

 place, after having been properly dried. Hydrochloric acid has the effect of 

 making flowers red that have been rendered green by the action of ammonia, 

 and also alters their appearance very sensibly. We may also mention, in 

 conclusion, that ammonia, combined with ether, acts much more promptly 

 than when employed alone. 



PHOSPHORESCENCE. 



Artificial flowers are frequently to be seen prepared in a particular 

 manner, which have the property of becoming phosphorescent in darkness, 

 when they have been exposed to the action of a ray of light, solar or electric. 

 These curious chemical objects are connected with some very interesting 

 phenomena and remarkable experiments but little known at the present 

 time, to which we will now draw the reader's attention. 



The faculty possessed by certain bodies of emitting light when placed 

 in certain conditions, is much more general than is usually supposed. 



M. Edmond Becquerel, to whom we owe a remarkable work on this 

 subject, divides the phenomena of phosphorescence into five distinct classes : 



1. Phosphorescence tlirough elevation of temperature. Among the sub- 

 stances which exhibit this phenomenon in a high degree we may mention 

 certain diamonds, coloured varieties of fluoride of calcium, some minerals ; 

 and sulphur, known under the name of artificial phosphorus, when it has 

 previously been exposed to the action of the light. 



2. PhospJiorescence through mecJtanical action. This is to be observed 

 when we rub certain bodies together, or against a hard substance. If we 

 rub together two quartz crystals in the dark, we perceive red sparks ; and 

 when pounding chalk or sugar, there is also an emission of sparks. 



3. Pliosphorescence through electricity. This is manifested by the light 

 accompanying disengagement of electricity, and when gases and rarefied 

 vapours transmit electric discharges. 



4. Spontaneous Phosphorescence is observed, as every one knows, in con- 

 nection with several kinds of living creatures, glow-worms, noctilucids, etc., 

 and similar phosphorescent effects are produced also with organic sub- 

 stances, animal or vegetable, before putrefaction sets in. It is manifested 

 also at the flowering time of certain plants, etc. 



5 . Phosphorescence through insolation and the action of light. " It consists," 

 says M. Edmond Becquerel, " in exposing for some instants to the action of 

 the sun, or to that of rays emanating from a powerful luminous source, 

 certain mineral or organic substances, which immediately become luminous > 

 and shine in the dark with a light, the colour and brilliancy of which depend 

 on their nature and physical character ; the light gradually diminishes in 

 intensity during a period varying from some seconds to several hours. When 

 these substances are exposed anew to the action of light, the same effect is 



