Take a Square Piece of Glass, about the size of a quarter of a sheet of Royal Paper, and fixing it directly between your Eyes, and the Objects you wou'd design, remove your self two thirds of your Arms-length, that is, about a Foot and a half backwards. Having then fixed your Head, by means of some Contrivance, so firm as not to move or shake a jot, shut one of your Eyes, and with the Point of a Pencil trace every thing upon the Glass, that you fee through it. When your Eyes are at liberty, you may transfer this Design from the Glass upon Paper, and chalking the Paper, make a fair Copy from it, to be put into Colours at your Leisure; but be sure to observe the Aerial Perspective.