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Of the Circle double.
WE must suppose that the first Circle A B, is that which we are now to make, and that we would give it a thickness or border, by making another more inward, in this manner: We shall give it such a bredth as shall please us, as A C, and from the center the great Demy-circle G we will draw the little one C D, which we will divide as the other great one, by drawing oc∣cult lines from the divisions of the Great unto the center G. And at the section of these lines of points of the Great, upon the less de∣mi-circle at the Points I, we must draw Perpendiculars I, as those that we have made in the great, upon the base; And to the end, that they may confound nothing, we must mark them with points from the points I, of the base, we shall draw to the point of sight F, of lines of points unto the line H K, and at their sections by the Diagonals, draw lines of points M N, which shall give round about the square the thickness G Q, which ought to have the whole circle. This done, we must draw lines from all the Angles of the great circle, reaching to the center, and where these shall cross the lines of points a b c d e f g h i k l m n o p q, which go to the Horizon, these shall be the Points, for to frame with the crooked lines the Circumference or round of the Inside.
He that would have a Plane of 3. 4. 5 or 6 Rounds, or Circles, in Perspective: He must set them in a Geometrical Plane, as the second is set there, and make all the same Operations,