OF GLASSES FOR OPTICAL PURPOSES. 39 



CHAPTER IV. 



\ 

 In what manor of forme to make Lookinge 



Glasses, to make any thinge shewe bigger then 



ytys. 



To make lookinge Glasses for to shewe any 

 thinge bigger then yt ys, That Glasse muste bee 

 made very large : for elles yt will not conteyne 

 any quantitye in sighte ; and this glasse must 

 bee Concave inwardes, and well pollyshed of the 

 hollowe or concave syde : and then the foylle 

 must bee layde on that syde that doth swell, as 

 a hyll, and bosse outwarde. And then this glasse, 

 the property of yt ys, to make all thinges which 

 are scene in yt to seem muche bigger then yt ys 

 to the syghte of the Eye, and at some appoynted 

 distance, from the glasse, accordinge to the 

 forme of the hollowness, the thinge will seeme at 

 the biggest, and so yow standinge nearer the 

 thinge will seeme less, vnto the sighte of the 

 eye : so that, accordinge vnto the forme of the 

 concavity or hollownes, and at some appointed 

 distance from hym that looketh into the glasse, 

 And yf that the glasse were a yearde broade, the 

 beame that shoulde come vnto his eye, shall 

 showe his face as broade, as the whole glasse, 

 And to see his face in this glasse, hee must stande 

 righte with the middle of the glasse, &c. And 

 these sortes of glasses ys very necessary for 



