428 History of Luminescence 



nomena connected with phosphorus luminescence, and will there- 

 fore be quoted at some length. 



The Aerial Noctiluca was actually a letter, written to and dedi- 

 cated to J. B. " a Virtuoso living in the Countrey, who has been for 

 many years absent from London ... to gratifie your curiosity about 

 the Phosphorus's, as much as I can without indiscretion at present 

 do." Boyle then explained that there were two sorts of phosphore: 

 " Those that may be stil'd Natural, as Glow-worms, some sorts of 

 rotten Wood and Fisches, and a few others, and those that are j^rop- 

 erly Artificial." The fact that they " without manifest heat shine in 

 the dark," distinguished them from " common Fire and Flame." Re- 

 garding the artificial phosphori there are " Bodies as shine only by 

 the help of External Illustration, or (if you please) such Bodies, 

 as being expos'd to the beams of the Sun," shine, and " another 

 sort, which needs not be previously illustrated by any external Lucid, 

 and yet continues to shine. . . ." The latter " by some Learned Men 

 has been call'd, to discriminate it from the former, a Noctiluca." 

 This division into natural and artificial luminescences is an early, 

 if not the earliest classification of cold lights, and was adopted by 

 all writers for many years afterwards. 



Boyle did not entirely approve of the designation " noctiluca " 

 which implied a light only at night but decided to use the word, 

 although reserving the right to speak of " a Selfshining substance, 

 which is more expressive of its nature: Of this substance Mr. Daniel 

 Krafft, a German Chymist, shew'd his Majesty two sorts or degrees 

 . . . the Consistent (or Gummous) Noctiluca " or as " tis call'd by 

 some in Germany, The Constant Noctiluca; which title it does not 

 ill deserve, since this Phosphorus is much the noblest we have yet 

 seen. . . ." 



" Besides this Gummous Noctiluca, Mr. Krafft had a Liquid one, 

 that perhaps was made by dissolution of the former in Water, or 

 some convenient Liquor." Boyle described " a third kind, that we 

 ourselves lately prepared . . . not the Body of the Liquor included 

 in the Vial, but an Exhalation or Effluvium mingled with the ad- 

 mitted Air . . . the Aerial Noctiluca. . . ." 



Boyle then discussed the practical value of the new material, as 

 follows: " The Uses that may be made of Noctilucas, especially of 

 the Consistent, are not, in probability, all of them to be easily fore- 

 seen and declar'd ... if the lucid vertue of the Constant Noctiluca 

 could be (as I see not, why it may not be) Considerably invigor- 

 ated," in the powder rooms of ships or " of use to those that dive in 

 deep waters; and also may very safely and conveniently be let down 

 into the Sea ... to draw together the Fishes that are wont to resort 



