p A r T IV. Of Things relating to Chymiftryf&t, 355 
When five or fix Drachms are fum’d away, take the Diih 
nitnbly out of the fire, fo foon as the Salt laft put in is dry. 
If you have wrought well, what remains in the Dilh will 
be yellowilh in fome parts, and every yellow part will ihine. 
Secure this Matter from the Air by fitting and cementing 
a Glafs to it: otherwife it will loofe its property 11a one 
Week. , ^ 
As to the Caufe of this ftrange Phenomenon, Dr .blare 
continues to this effect. I (hall in Ihort offer my Thoughts, 
and refer them to your Judgment. TwoQueftions may 
arife: What it is in this Mixture that yields the light ? and, 
How it doth it ? As to the firft, I take it to be the pure fiery 
part of the Spirit of Nitre embraced by the Chalk For 
that the reft is weak and phlegmatick 5 as appears, if it be 
diftilfd Alfo, that about the end of the Operation, a black 
Fume begins to rife and fly away. That it by continuing 
the Dilh too long in the fire, you drive all the Nitrous parts 
► away, the Chalk which flays behind will not be luminous 
Or if the Matter duly prepar’d, be expofed to the Air, and 
thereby prey’d upon, the fame effect will follow. 
As to the Second, I fuppofe, That it (lames not by Imbi¬ 
bition of Light, but by Impreflion from it, from whence 
proceeds a motion therein productive of Light. Which 
we may the rather be induced to believe, In that if it be 
put into an Iron Cover, and then an Iron Box, and a good 
heat given to it, it will fhine fo vigoroufly as to feern to 
kindle the Air about it. That two Men by following their 
blow clofe, will make a Bar of Iron glow, or fhine in the 
dark. And although the Impulfe of Light may feem finally 
yet upon Bodies nearly related to it, as This feemstobe, it 
appears to be great. As in thofc odd effects it fometimes 
hath upon Infants unus’d to it 5 and People that have fore 
Eyes; or have been newly Couch’d 3 as it happen d to 
Dr. C a file fometime fince, who by making bold with his 
Eyes too early, ( i. e. by a too frequent admiflion of light 
to them,) after that Operation, did thereupon fuff er fuch 
extreme pains, and mifclnef in his Eyes, that he now difpairs 
of ever feeing more. , A 
Mr. Haac (a\ faith he, hath frequently repeated the 
following Experiment upon this Phofphorm. If it be ex- nmm H p on 
pofed to the Morning Light a little before Sun nfing, it 
r Zz 2 prefents J 5 s 
