188 History of Luminescence 



were finally replaced by Lavoisier's terminology. The new theory 

 of combustion represented a true revolution in thought and may be 

 regarded as the beginning of the modern era of chemistry. 



During the middle and latter part of the eighteenth century, even 

 after Lavoisier's discoveries phlogiston was invoked to explain many 

 types of luminescence. Wiegleb's views have already been given. 

 Benjamin Wilson in 1777 thought that oyster shells, which become 

 phosphors on calcination, received phlogiston from bodies they 

 touched in the crucible. The article on " phosphores " (1778) of 

 the French Encyclopedie called Kunkel's phosphorus a " perfect sul- 

 phur composed of phlogiston and acid," and Scheele declared: " heat 

 . . . made very elastic by the addition of phlogiston, penetrates 

 likewise into them [phosphors]." 



Bryan Higgins, iVL D., wrote A Philosophical Essay Concerning 

 Light (London, 1776) , in which he attempted to show that " A 

 motion of light is necessary toward illumination and vision " by 

 observations of the element, phosphorus. He wrote: 



The phosphorus of Kunkel causes no illumination whilst it is kept 

 in the Torricellian void, and whilst it is by any means prevented from 

 emitting its phlogiston. The same phosphorus illuminates, more or less, 

 as the quantity of phlogiston which escapes from it, in a given time, is 

 greater or less; and the illumination ceases when the phlogiston is de- 

 parted from the residual incombustible saline matter, with which the 

 fresh phlogiston of any phlogistic body is capable of forming phosphorus 

 again. And since the phosphorus is luminous only whilst matter is mani- 

 festly moved from it; we clearly perceive that Light at rest, whether in 

 the phosphorus or diffused in the chamber, is not sensible to us; and 

 that the illumination caused by phosphorus consists in the motion of 

 Light emitted from the phosphorus or in the motion which diffused or 

 quiescent Light receives from the moved phlogiston of the phosphorus. 



George Adams in Lectures on Natural and Experimental Phi- 

 losophy (1794) believed that " phosphorctic and phlogistic bodies 

 agree in containing a quantity of light," the latter necessitating " an 

 exposure to the atmosphere " and being greatly changed " on abstrac- 

 tion of their luminous matter," the former not requiring air and 

 remaining unchanged after their light (regarded as a material sub- 

 stance) had disappeared, 



Lavoisier's studies on combustion and animal respiration stimu- 

 lated a host of later workers to try the effect of gases on luminescent 

 materials— phosphorus, phosphors, luminous wood and fish, fireflies, 

 and glowworms, etc. The papers appeared between 1782 and 1800. 

 Among the dozen men carrying out this work, only two, G. Forster 

 (1782) and F. Achard (1783) , used the word " dephlogisticated air " 



