A TREATISE 



r object through the glafle in an other pofition or fituation ofit r 



The rcafon namely, if we rayfe it fo high , that we muftlooke upwards to 

 whythcprifme fee the object ; which thereby appeareth above us .-whereas in 

 pofcuon, tne former fitnation, it came in through the lower fuperficies, 

 rea pcare ^ we ^^ cc ^ downe to it, and it appeared under us:fbr in this 

 'contrary fecond cafe, the objects comming into the glaiTe by a fuperficies. 

 to whar they not parallel as before, but (leaping, from the objectwards : it 

 did , when it g)jioweth,that the neerer the object is, the lefler mud the angle 

 was in an other be^^h j t maketli with the iitperficies ; contrary to what hap- 

 pened in the tormer cafe : and likewise, that if from one point 

 of the neerer .object, there fall two rayes upon the glaffe, the 

 ray that falleth uppermoft, will make a lefler angle, then the 

 other that falleth lower : and to, by our former difcourfe, that 

 point may come to appeare in the fame place with a point of the 

 iiirther objed;and thereby make a middling colour. 



So that in this cafe, the white which is neerer, will mingle his 

 feeble pidture with the black that is further off : whereas before 

 the black that was further off , mingled his feeble fhadow with 

 the ftrong picture of the neerer white. Wherefore by our rule 

 we borrowed of the painters, there will now appeare a blew on 

 the further end of the paper, where before appeared a red ; and 

 by coufequence on the neerer end a red will now appeare, where 

 in the former cafe a blew appeared. Thiscafewehavecho/en., 

 as the plainefl to fhcw the nature offuch colours : out of which 

 he that is curious , may derive his knowledge to other cafes, 

 which wee omit ; bccaufe our intent is onely to give a gene- 

 rail doctrine , and not the particulars of th Science : and ra- 

 ther to take away admiratioa.then to inftruct the Reader in this 

 matter. 



6. As for the various colours,which are made by ftrayning lioht 



The reafon through a glafle, or through ibme other Diaphanous body ; to 



olours V ?"e- ^ ovcr [ ' ie ca "f es an< ^ variety of them, we muft examine what 



neraUby "pure things they are that do concurre to the making of them : and 



light paffing frhat accidents may arrive unto thofe things, to vary their pro- 



through a duct. It is cleare,that nothing interveneth or concurreth to the 



prifmc. producing of any of thelecolours,bcfides the light it felfe which 



is dyed into colour, and the glafle or Diaphanous body through 



which it paflcth.In them therefore,and in nothing elfc,wc are to 



make our enquiry. 



To 



