[477] 
one point ( or rather iffiie out from one point ) ot the Ob- 
je£l ftanding at fuch a due diftance, as the perfon may 
clearly and diftindly fee it, or according to his length of 
Sight (as ABC, ia the firft Fig.) 
And thckSpeBacles may be fuppofed better for preferv- 
ing the Sight, then the ordinary ones with Glaffes becaufe 
they reprefent theCbjed more naturally.and withal more 
clearly and diltindly to the Eye,then the other, whofe re- 
fraded raies being coUeded together with the right ones 
in the Glaffes, do fomewhat confound good Vifioui as be- 
fore. Efpecially if the vifive power be ftrong enough to 
be fufficiently determin d by the right raies alone. 
Fori fpeak now of preferving a good Eye by thefe 
Spedacles; which holds in proportion true alfoof a bad 
one. Becaufe thofe Raies ( both right and refraded) be- 
ing coUeded and brought lo near the Eye ( whether good 
or bad ) as the Spectacles are uffaally plac d, do too much 
affed it, both by their own brightnefs, and alfo by the 
brightnefs of the colours of the Objed ( when they are 
bright) which is brought very near alfo ; whereby the 
Eye is dazl'd and confounded ^unlefs there be a ftrong at- 
tention and conatus of the Spirits, whereto the bright 
Raies do certainly engage them ; which of neceffity wea- 
kens Vifion 5 efpecially if thefe Glafs-fpedacles be much 
us'd. . 
- Wherefore the now defcrib'd new Tube-fpedacles, con- 
tributing fo much to the help and prefervatioa of Sigh ', 
may well be counted an improvement of DireH; Vijion ; 
becaufe they convey the raies to the Eye without any 
kind of refradion whatfoever. Seeing the fame Objed al- 
fo through various holes, plac'd at certain diftances, 
does fomewhat alter Vifion , but of this perhaps more 
hereafter. 
Now as D/WS ^f/f<?;^has thus been improv'd ; fo like- 
wife DireU Hearing partly has already receiv'd, and part- 
lymay('by the Dodrine whereof we are treating, if well 
cui- 
