The Eighteenth Century 169 



Wiegleb began his chapter on " Phosphori " in a section dealing 

 with " Philosophical Chemistry," as follows: - 



Fire is divisible into Light and Heat, which are two real chemical, and 

 therefore physical, elements quite distinct from each other. . . . Some 

 bodies attract the light and give it off afterwards (light magnets) .... 

 Other bodies in which the light is fixed in the form of phlogiston, 

 give it out only in certain degrees of heat, and in consequence of being 

 exposed to the air . . . properly termed Phosphori, or bearers of light. 



Each of these Classes of Bodies may be distinguished into natural and 

 artificial. 



The diamond was classified among the natural and the best known 

 artificial light magnet was the prepared Bolognian Stone. Wiegleb 

 then gave a considerable account of the Bolognian phosphor and 

 other varieties, such as Baldouin's and Canton's phosphorus, and 

 finally remarked, " No one has ever been able to explain the real 

 cause of the power of attracting light in a satisfactory manner." 



Among the " Phosphori, properly so called, . , . the natural abound 

 in different parts of the animal creation " (glowworm, elaters, Ful- 

 gora, sea pens, worms, medusae, Pholas dactylus and various bodies 

 when in a state of decomposition— veal, fish and wood) . " With re- 

 spect to genuine artificial Phosphori, there is but one species known 

 at present, viz. the Phosphorus of Urine." Then followed a long 

 account of phosphorus and methods of preparing it, with special 

 mention of the work of Marsroraf, Wies'leb continued: 



'&o' 



Instances of imperfect phosphori are Romberg's Phosphorus and lump 

 sugar, which light when struck, and fluor spar and Scharfenburg blend 

 " which can emit a phosphoric light merely on the application of heat. 



Having admitted that an explanation of the attraction of light is 

 difficult to explain, neverthless Wiegleb made an attempt. Apply- 

 ing his own view that there are ten classes of substances— heat, lieht, 

 water, earth, salts, metals, combustibles, mephitic gas, and magnetic 

 fluid— and that phlogiston is light and heat plus a substance com- 

 bined with them, while fire is light and heat combined but without 

 a substance, he wrote: 



It should seem indeed that the state of privation of air, into which the 

 ponderous or calcareous earth [i. e., the Bolognian stone before calcina- 

 tion] is put, by being treated in fire by the substances that are added 

 to it, must make it fit to attract the light ab extra; the added substances 

 however must necessarily contribute something to this, as pure calcareous 

 earth deprived of air does not posses this property. ... It is probably 



-" Quotations from the English translation (1789) , pp. 612-620. 



