432 History of Luminescence 



noctilucal matter, it seemed to be kindled into an actual flame, 

 that afforded a very vivid light; which success pleased me the better, 

 because it shewed, that a kind of fire may be kept under water, as 

 long as one pleases, without sensible burning, . . ." 

 In conclusion, Boyle wrote: 



Light is so noble a thing, that the matter our phosphorus affords it to 

 reside in being endued with some uncommon qualities, and particularly 

 with a strange, and almost incredible subtility of parts, I cannot but 

 hope that ... [in the future] something would be produced, tending to 

 the discovery of the nature, not only of light but divers other bodies, 

 and perhaps also, of good use to human life. If some unwelcome circum- 

 stances did not, for the present, discourage me, I would contribute my 

 weak endeavors toward such a design. 



One of the extraordinary phenomena connected with phosphorus 

 is a periodic luminescence of the vapor when kept in a partially 

 confined space. This was observed by Boyle and also described by 

 " the Ingenious Fred. Slare M. D." (1683) , who tried many experi- 

 ments. He referred to it as " A Parallel hetivixt Lightning and a 

 Phosphorus " and continued, 



In order to the keeping my solid Phosphorus from consuming, I usually 

 plac'd it at the bottom of a Glass of Water: having several of these 

 Glasses disposed upon a Table in view whilst I lay upon my Bed, I could 

 observe several flashes of Light that successively past through the Water, 

 and made such bright, and vigorous Coruscations in the Air, as would 

 surprise and affrighten one not used to the Phenomenon. This fiery 

 Meteor passes something contracted through the incumbent Water, but 

 expands itself much as soon as it gets above it. 



Slare went on to point out that the above effect was pronounced in 

 warm weather and he never noticed it in winter as " the season of 

 the Summer is most productive of Lightning." 



Slare also studied the behavior of phosphorus in absence of air in 

 an article published in the Philosophical Collections (No. 4: 81, 

 1681-1682) . He wrote: 



It being now generally agreed that the fire and flame of phosphorus 

 have their pabulum out of the air, I was willing to try this matter in 

 vacuo. To effect this I placed a considerable lump of this matter [phos- 

 phorus] under a glass, which I fixed to an engine for exhausting the 

 air; then presently working the engine, I found it to grow lighter [i. e., 

 more luminous], though a charcoal that was well kindled would be quite 

 extinguished at the first exhaustion; and upon the third or fourth 

 draught, which very well exhausted the glass, it much increased the 

 light, and continued to shine with its increased light for a long time; 



