OF GLASSES FOR OPTICAL PURPOSES. 45 



CHAPTER IX. 



The effects what may bee done with these two last 

 sortes of glasses: The one concave with a 

 foyle, vppon the hylly syde, and the other 

 grounde and pollisshed smoothe, the thickest in 

 the myddle, and thinnest towordes the edges or 

 sydes. 



For that the habillity of my purse ys not able 

 for to reache, or beare the charges, for to seeke 

 thorowly what may bee done with these two 

 sortes of Glasses, that ys to say, the hollowe or 

 concave glasse : and allso that glasse, that ys 

 grounde and polysshed rounde, and thickest on 

 the myddle, and thynnest towardes the sydes or 

 edges, Therefore I can say the lesse vnto the 

 matter. For that there ys dyvers in this Lande, 

 that can say and dothe knowe muche more, in 

 these causes, then I : and specially Mr. Dee, 

 and allso Mr. Thomas Digges, for that by theyre 

 Learninge, they have reade and seene many moo 

 auctors in those causes : And allso, theyre ability 

 ys suche, that they may the better mayntayne 

 the charges : And also they have more leysure 

 and better tyme to practyze those matters, which 

 ys not possible for mee, for to knowe in a nombre 

 of causes, that thinge that they doo knowe. But 

 notwithstanding upon the smalle proofe and ex- 

 peryence those that bee but vnto small purpose, 



