OF BODIES,Chap.XXXI. 327 



in the further cone 5 for both fides being equally fituated to 

 the courfe of the light , within its ovvne cone , there is nothing 

 to vary the colours, but onely the f Jrength and the vveakneflc of 

 the two lights of the cones , on this fide , and on that fide the 

 point of concurle : which point , being in this cafe the ftrong 

 and cleare light whereof we made general! mention in our 

 precedent note, the cone towards the glafle and the illuminanr, 

 is the Wronger fide^and the cone from the glafle.is the weaker. 

 In thofecafes,where this reafbn is not concerned, we fhall fee 

 the viciory carried in the queftion of colours , by the ihady fide 

 of the opacous body: that is, the blew colour will ftill appeare on 

 that fide of the opacous bodies Shadow that is furthest from the 

 illuminant. But where both caufes doe concurre and contra/I 

 for precedence , there the courle of the light carrieth it : that is 

 to fay_,the red will be on that fide of the spacous bodies fliadow 

 where it is thicker and darker, and blew on the other fide where 

 thefliadow is wot fo ttrong; although theftiadow becaft that way 

 that the red appeareth : as is to be feen, when a (lender body is 

 placed betwixt the priimeand the refle&ent body, upon which 

 the light and colours are call; through the prilme : and it is evi- 

 dent, that this caufe of the c*urfe of the fliadow,, is in it felfa 

 weaker caufe,, then the other of the courfe of light , and muft 

 give way unto it whenfoever they encounter (as it can not be 

 expedlccf,but that in all circumtfanees.fiiadows fhould be light^) 

 becaufe the colours which the glafle cafkth in this cafe, are much 

 more faint and dusky then in the other. 



For effects of this latter caufe , we fee that when an opacous 

 body lyeth crofle the prilme^ whiles it ftandeth end-waies, the 

 red or blew colour will appeare on the upper or lower fide of its 

 picture,, according as the illuminant is higher or lower then the 

 tranfverfe opacous body : the blew ever keeping to that fide of 

 the picture, that is furtheft from the body , and the illuminanc 

 that make it: and the red the contrary ; likevvile if an opacous 

 body be placed out of the axis,in either of the cones wehave ex- 

 plicated before, the blew will appeare on that lide of the picture 

 which is furtheft advanced in the way that the fliadow is 

 caft: and the red,on the contrary : and fb, if the opacous body 

 be placed in the firft cone ( befide the axis) the red will appeare 

 on that fide of thepi&nre in the bafis of the fecond cone, which 



is 



