[ 107 ] 

 CHAP. VIII. 



PUOsPHORESCENCU, OR SPONTANEOUS ILLUMINATION, 

 ANIMAL, VEGETABLE, AND MINERAL. 



1 ins is a most extraordinary and interesting subject, and a perusal 

 of the three precefling chapt* rs will, in a considerable degree, en. 

 able the reader to understand its general principles, though there is 

 much that has hitherto eluded pursuit, and still remains to be deve- 

 loped. 



Phosphorescence, in its broadest latitude, imports light thrown 

 forth from substances that at the same time emit little or no heat at 

 the common temperature of the atmosphere, and which are deno- 

 minated phosphoric. 



The phosphorus properly so called, and which is usually under, 

 stood in chemical books, and employed in chemical processes, is 

 that commonly known by the name of Kunckel's phosphorus, and 

 which we shall describe under that designation. But there are 

 various other substances that possess, in different degrees, the same 

 kind of illuminating power, and which it is hence necessary to 

 take some notice of, as well as of the effects they produce. 



Of these kinds the phosphorescent substances there are three 

 leading divisions. The first comprehends those which require a 

 previous exposure to the solar or other light, in order to become 

 luminous; whence they are calkd solar phosphor!: the second in- 

 cludes those which, without any necessary previous exposure to 

 light, be come luminous when moderately heated, which are deno. 

 minated calorized phosphor!, or phosphor! from heat : the third 

 comprehends those substances belonging to the animal and vege- 

 table kingdoms, which emit li_ht spontaneously at the common 

 temperature, without the necessity of a previous exposure to light) 

 and these are called spontaneous phosphor!. 



SECTION I. 



Solar Phosphori. 



A CASUAL discovery by Vincenzio Cascariolo, a shoemaker of 

 Bologna, about 1630, was the first circumstance that attracted the 

 notice of philosophers to this curious subject. This man being in 



