MacrocRapuha, 
honourable Mr. Boyle, », What maysbe faid of thofe dgwes fatui: that ap: 
pear inthenight.I cannot fowell affirm, having never had the opportunis 
ty to.examing them my felf, nor tobe inform’d by‘any others thatohad 
obférv’dthem:) And the relations’ of them in Authors ‘are fo im perfect, 
that nothing:can be built omthem. | But Dhope Ithall beable in another 
place tomake it at leait very probable, that there is-even in tho alfoa 
Motion whi¢h caufes this efiect. ‘That the thining of s¢a-mater proceeds 
from thefame caufe, may be argued from this, That» it fhines:not till ei+ 
ther it: be beaten againita Rock, or befome otherwayes brokemoragi- | 
tated by Storms, or Oars, or other percuffing bodies.:' And thdrthe As 
nimal Exergyes or Spirituous agil parts’ are: very active‘in Cats: eyen when 
they fhine, ‘feems evident shoud becaufe their ‘eyes never thine bute 
when they look very intently either to find their prey, or bemgihunted. | 
in a dark room,whenthey {eek after their adverlary; or to find awayto - 
efcape.: And the like may be faid of the thining: Bedies of Gloworms, 
fince ‘tis evident they can at pleafure either increafeicr extinguith that 
Ruadioviiniy insipsisos dium buedio ft te Sigel oct ylineupsinias 
It would be fomewhat too long a work for this place Zeteticallp to: 
examine; and pofitivelyto prove, what’ particular kind of motionit is 
that muit be the efficient of Licht ; for though it be! amotion,; yet ‘tis 
not every motion that producesit, fince we find there are many: bodies 
very violently mov'd, which yet afford not fuch ameffed 5 and there 
are other bodies, which to our other fenfes, feem not mov'd fo tiuch, 
which yer'fhine. -Thus'Water and quick-filver,and: moft other liquors 
heated, fhine not; and féeveral hard bodies, as Iron, Silver, as Sk 
per, Wood, ¢c. though very often ftruck with a hammer, thine not pre= 
tently, thoughthey will all of them grow exceeding hot 5 whereas rot= 
ten Wood, rotten Fifh, Sea water, Gloworms, &c. have nothing of tan- 
gible heat inthem, and yet ( where there is no ftronger light to affeé the 
Senfory) they fhine fome of them fo Vividly, that one may make a fhift 
toread by them. . © j 20D. ery sommiisg xd 
It would'be too long, Tay, here:to infert the difcurfive eh fy 
which I inquir'd after the proprieties of the motion of Light, ‘and there= 
fore I thall only add the refalt..cic 901 aoc SneNat omer atin noo 
And, Firft, I found it ought to be exeeeding gxick, fuch as thofe moti- 
ons of fermerxtation and putrefattion, whereby, certainly, the parts are 
_ exceeding nimbly and violently mov'd ; and that, becaufe we hind thofe 
motions are able more minutely to fhatter and divide the body,then the 
moft violent heats or menflruums we yet know. And that fire is nothing’ 
elfe but fuch a diffolution of the Burning body, madeby the molt aniver- 
fal menftrium of all fulphurcons bodies, namely, the Air, we fball in an 
other place of this Tractate endeavour to take probable. And that, 
in all extteamly hot thining bodics, there is a very quick motion that 
_ caufes Light, as wellias ‘a mote robuft that caufes Heat, may be argued 
from thecelerity wherewith the bodyes are diflolv’d. = pa 
Next, it mult be a ¥ibrative motion, And for thisthe newly mention’d 
Diamond affords us agood argument 5 finee if the motion of the parts did 
not 
