<«p) 
His Theoryi of Apertures, though he feems to think it very an- 
thentick, yet to me it feems not fo cleer. For, the. fame Glafs 
will endure greater or XeGer Apertures, according to the lefifer 
or greater Light of the ObjeH : If it be for the looking on the 
Sun or Venus, or for feeing the Diameters of the Fix'd Stars ,fhea 
(mailer Apertures do better j if for the Moon in the daylight , or on 
Saturn, or Jupiter., or Mars , then the largeft. Thus I have often 
made ufe of a 12 foot-Glafs to look on Saturn with an Aperture 
of almoft 3 inches, and with a (ingle Eye-glafs of 2 inches dou - 
tie convex: but, when with the fame Glafs I looked on the 
Sun or Venus , I ufed both a (mailer Aperture , and lhallower 
Charge. And though M. Au^out feems to find fault with the En~ 
gliJbG lafs of 36 foot,thathad an Aperture of but mchts French} 
as alfo, with a 60 foot Tata?, ufed but with an Aperture of 3 inch- 
es; yet Ido not find, that he hath feen Glaffes of that Iengch 3 that 
would bear greater Apertures 5 and 'tis not impoffible , buthis 
Theory of Apertures may fail in longer Glaffes. 
Of a me am to illuminate an ObjeB in mb at pro- 
portion one pleafeth ; and of the Dijlancey re- 
quifite to burn Bodies by the Sun. 
One of the means ufed by M. Au^out to enlighten an Objed, 
in what proportion one pleafeth 3 is by (ome great OhjeU-Glafs , 
by him called a Planetary one, becaufe that by it he (hews the 
difference of Light, which ail the. Planets receive from the Sun, 
by making ufe offevera! Apertures, proportionate to their di- 
ftance from the Sun, provided that for every 9 foot draught, or 
thereabout, one inch of Aperture be given for the Earth. Doing 
this, one fees {faith he ) that the Light which Mercury receives, 
is far enough from being able to burn Bodies, and yet that the 
fameLightis great enough in Saturn to fee cleer there, feeing 
that (to him) it appears greater in Saturn, than it doth upon our 
Earth, when it is overcaft with Clouds : Which (he adds) would 
fcarce be believed, if by means of this Glafs it did not fenfibly 
appear fo > Whereof he promiles to difcourfe more fully in his 
K ' Treatife 
