Part IV. Of Things relating to Chymijlryj&c. 555 
When five or fix Drachms are furn d away, take the Dilh 
nimbly 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 yellowifh in fome parts, and every yellow part will fhine. 
Secure this Matter from the Air by fitting and cementing 
a Glafs to it : otherwife it will loofc its property in one 
Week. 
As to the Caufe of this ftrange Ph<enome?ion, Dr. Slare 
continues to this effect. I fhall in fhort offer my Thoughts, 
and refer them to your Judgment. Two Queftions 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 Sprit of Nitre embraced by the Chalk. For 
that the reft is weak and phlegmatick 3 as appears, if it be 
diftiird. Alfo, that about the end of the Operation, a black 
Fume begins to rife and fly away'. That if by continuing 
the Difh too long in the fire, you drive all the Nitrous parts 
away, the Chalk which flays behindrwill not be luminous. 
Or if the Matter duly prepared, be expofed to the Air, and 
thereby prey'd upon, the fame effect will follow. 
As to the Second, I fuppofe, That it fhines not by Imbi- 
bition of Light, but by Impreffion 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 ihine fo vigoroufly as to feem to 
kindle the Air about it. That two Men by following their 
blow clofe, will make a Bar of Iron glow, or (bine in the 
dark. And although the Impulfe of Light may feem fmall 5 
yet upon Bodies nearly related to it, as This feems to be, it 
appears to be great. As in thofe odd effects it fometimes 
hath upon Infants unus'd to it 3 and People that have fore 
Eyes 5 or have been newly Couch'd 3 as it happen d to 
Dr. Caftle fometime fince, who by making bold with his 
Eyes too early, ( u e. by a too frequent admiffion of light 
to them, ) after that Operation, (did thereupon fuffer fuch 
extreme pains, and mifchief in his Eyes, that he now difpairs 
of ever feeing more. 
Mr. Haac (a) faith he, hath frequently repeated die ^)^*« 
following Experiment upon this Phofphorus. If it be ex- riw ^ e ^" 
pofed to the Morning Light a little before Sun rifing, it *be Load- 
Z7.2 prefents^ Pjrt 3- 
