110 ANIMAL AND VEGETABLE PMOSPHOHI. 



SECTION II. 

 Colorized Phosphori. 



BESIDES those substances (hat are phosphorescent by exposure ( 

 the ray s of the sun, there are others which give out light when sim. 

 ply heated. These materially differ from the former in this circum- 

 stance, that after having been continued at any particular tempe- 

 rature till their luminousm vs i* exhausted, they are. incapable of 

 becoming again luminous, except at a greater heat than that to 

 which they were first subjected. The range of temperature at 

 which these bodies become luminous is not very extensive, com- 

 mencing at about 400 Fahr. and terminating at the lowest visible 

 red heat. The following is a lit of substances exhibiting this, 

 properly arranged by Mr. S. Wedge wood, according to the bril. 

 liancy of the light. 



That variety of the blue fluor spar of Derbyshire, which, when 

 scraped or struck, emits a fetid, bituminous odour, is the most phos- 

 phorescent by heat of all the known substances: it glows, when 

 moderately heated, with a pale emerald green light, sufficiently 

 intense to be Tery visible even in daylight. To the second rank 

 belong the common swine-stone, the common blue fluor, and red 

 fel.spar, all which, as well as the following, exhibit a white or red. 

 dish light. The third class includes the diamond, the ruby, carbo. 

 nated baryte, chalk, colourless calcareous spar, sea-shells, granite, 

 and white fluor. The fourth class comprehends white sand, car- 

 bonated magnesia, heavy spar, flint, white marble, quartz, porcelain 

 and earthen ware. The fifth class includes most of the metals, 

 sulphat of potash, borax, white paper, white linen, sawdust, and 

 asbestos. Under the sixth and last class are comprehended oil, wax, 

 spermaceti, and butter when boiling or nearly so. Most of these 

 are also phophorescent by friction. 



SECTION III. 



Animal and Vegetable Phosphori. 



IT is a curious fact, and though occasionally noticed, not gene, 

 rally attend <! to till of late years, that various animal and vegetable 

 substances hare a power of throwing forth light under particular 



