Page:Philosophical Transactions - Volume 003.djvu/120

 any one, that hath any insight in the Opticks, may easily direct. The nearer it is placed to the object, the more is the Object magnified on the Wall, and the further off; the less; which diversity is effected by Glasses of several spheres. If the Object cannot be inverted (as 'tis pretty difficult to do with Living Animals, Candles, &c.) then there must be two large Glasses of convenient Spheres, and they plac'd at the appropriated distances (which are very easily found by tryals) so as to make the representations erect as well as the Object.

These Objects, Reflecting and Refracting Glasses, and the whole Apparatus; as also the Persons employ'd to order, change and make use of them, must be placed without the said high Window or Hole, so that they may not be perceived by the Spectators in the room; and the whole Operation will be easily perform'd.

The particular manner of preparing the Objects, adapting the Glasses, collecting the Rayes of the Sun, varying the Object, making the representations of the Sky (by the help of other Glasses) and of Clouds (by the help of Smoak) &c. I intend, hereafter, when I have leisure and opportunity, more particularly to describe; as also the way, of making a natural Landskip, &c. to appear upon the walls of a light room; which will not only be very pleasant, but of great use in painting. Whatsoever may be done by means of the Sun-beams in the daytime, the same may be done with much more ease in the night, by the help of torches, lamps, or other bright lights, plac'd about the Objects, according to the several sorts of them.

So far our Inventor; who hath not contented himself with the bare speculation, but put the same in practice some years since, in the presence of several members of the R. Society, among whom the Publisher had the good fortune to see the successful performance of what is here answered.

SIR, You may perchance remember, that some time since, Rh