(743) 
a&yone, that hath infighc in the Ofticfo, may eafily direct. 
The nearer it k placed to the objeCt, the more is the Objedi ma- 
gnified on the Wall, and the further ofF 5 the lefs $ which diverfi- 
ty is effected by Gaffes offeveralfpheres. If the Objeft cannot be 
inverted^ us pretty difficult to do with Living Animals, Can- 
dles. &c) then there muft be tm large GtefTes of. convenient 
Spheres,and they plac'dat their appropriated diftances (which are 
very eafily found by tryals) fo as to make the representations 
as well as the ObjeCt. 
Thefe ObjeCis, Refie&ing and Refracting Glafies, and the 
whole Apparatus \ as alfo thePerfons employ 'd to order, change 
and make ufe of them, muft be placed without the faid high 
Window or Hole, fo that they may not be perceived by the Spe- 
ctators in the room $ and the whole Operation will be eafily per- 
form'd. 
The particular manner of preparing the Objects, adapting the 
GlaflfeS; collecting the Rayes of the Sun, varying the ObjeCt, 
making the reprefentations of the Sky (by the help of other 
Gaffes) and {of Clouds ( by the help of Smoak ) &c. I in- 
t end, hereafter, when I have leifure anci opportunity, more par- 
ticularly to defcribe $ as alfo the way, of making a natural Land- 
skip, &c. to appear upon the walls of a light rooms which will 
not only be veiy pleafant, but of great ufeln painting. What- 
foever may be done by means of the Sun- beams in the day* 
time,the fame may be done with much more eafe in the nighty 
by the help of torches, lamps, or other bright lights, plac'd about 
the ObjeCls, according to the feveral forts of them. 
So far cur Inventor 5 who hath not contented himfelf with the 
bare speculation, but put the fame in practice fome years fince, 
in the prefence of feveral members of the K.Soeiety, among whom 
the Pubhfhcr had the good fortune to fee |the fuccefsful perform- 
ance @f what is here delivered. 
An Email of a Letter lately written by Mr. S. Colepreffe, from 
Leiden, to the Publifher, about the" making of counterfeited Opal, 
and the Recovery of the Art ef making Red-glafs. 
Sir, You topy perchance remember, that fome time fince, 
Nnnn 2 there 
