With a plain and Concave-Glass, make an Image be seen hanging altogether in the Air.

Do thus. I said that by help of a Concave-Glass, an Image may be sent forth: and this is seen by none but those that stand over against it; Set the Concave-Glass to your brest, without the Centre place a Poniard against it, and going farther off, set a plain Glass against it; and looking in that, you shall see the Image reflected from the Concave-glass, hanging in the Air, and that exactly. But if an ingenious man observe it, he may wonderfully see an Image hanging in the Air, that is received in a plain Glass, and sent far out as I shewed, without the help of a Concave-glass, and a visible spectacle, by the means of a plain Glass onely. You may also