(t So%9 ) 
whofe parts are |iike fo many fragments of faeh Platei* 
Xhefe feem to be the moft plain^ genuine and necelTary 
conditions of this {dypothefr. And they agree To juflrly with my 
Theory, that if the Animadverfor think to apply them, he 
need not, on that account , apprehend a divorce from But 
yet how he will defend it from other difficulties^ 1 know not. 
Forj to me, the Fundamental Suppoficion it leif feems impof- 
fible ^ oamelyjThatthe Waves or Vibrations of any FluidjCan^ 
l^ke the Rays of Light^ be propagated in Stretghi lioes^withoul 
a, continual and very extravagant fpreading and beading every 
way into thequieicent Medium^ where they are terminated 
byk. 1 miftake, if there be not both Experiment aod De. 
monftratioD to the contrary* And as to the other two or three 
HypQthefesy which he mentions, 1 had rather believe them fob- 
jett to the like difScoltieSjthan fyfpe^l thtJmmadverfj^ flipuld 
ielecSlihe worft for his owa* 
What i hive (aid of thisj may be eafily applied to all other 
Mechmiical Hypothsfes, in which Light is fuppofed to be caufed 
by any Preffion or Motion whatfoeverj excited in the ^ther by 
the agitated parts ofLnminous bodies*For.,it feems impollible^ 
that any of thofe Motioos or Preffions can be propagated in 
lines without the like fpreadi^g xyery . way into the 
fliadow'd Medinmj on which they border, . But yet, if any 
man c^n think it poffible, be iiiuft at leaft ^lloWjthat tkofe Mo»- 
tions or Endeavors to motionj caufed in the sti^r by the feve- 
ral parts of any Lncld body that differ in fize^figijre^ and agi-^ 
tation^muft neceffariiy be uneqaal • Which is enough to de- 
nominate Light an Aggregat oi ^/(pr^ ray% aecordiog to any 
ofthofe Hypotbeles^, And if thofe Original inequalities may 
fuffice to difference the Rays in Colour and Refraiigibiiity, I 
fee no reafon, why they^ that adhere to any of thofe hypothefes^ 
fliould feek for other Chafes of thefe Effeftjj unlefs (to ufe the 
Objectors ^xgumtm^ they will multiply ' entities without ce» 
ceflity» 
The f^iri thing to be confidered is, the Condition of the 
Animaduerj^fs ConctiSiQ^^^vihxcl-i 
is, that I would explicate mvJheo* Animac^ verfbr's Comef;^ 
Ties by his Hypothefis: And it I could tt^s^ 
comply with him io that pcipi ^ 
' there 
