Whittock, Nathaniel: The Oxford Drawing Book, Or The Art Of Drawing, And The Theory And Practice Of Perspective: In A Series Of Letters Containing Progressive Information On Sketching, Drawing, And Colouring Landscape Scenery, Animals, And The Human Figure: With A New Method Of Practical Perspective: Detailed In A Novel, Easy, And Perspicuous Style, For The Use Of Teachers, Or For Self-Instruction. Embellished With Upwards Of One Hundred And Fifty Lithographic Drawings, From Real Views, Taken Expressly For This Work (Oxford , London, 1825)

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seen at all, only produce a dim confused effect. You will understand this by refer-
ring to No. 1. Plate XV.
C is the point of distance, or spot where the person stands to take the view; A is
the point of sight in the horizon ; b b are the points of distance on the horizontal line,
formed by the lines or rays from C. You will observe that all that comes within
these lines, may be seen distinctly, but if you wished to take in a greater extent of
country, you could not do it from the same point of distance without turning the
head, and thus having another point of sight, which would throw your whole draw-
ing into confusion: but if you were to stand at a greater distance, the angle would be
larger, and would take in more of the view; and the points b b, would in this case
be a greater distance from the point of sight. This drawing will, it is hoped, shew
you why the points of distance are placed on the horizontal line: and we will now
proceed to their use in perspective drawings.
In No. 2. Plate XV. d is the base line; and I wish to put a square in perspective,
one side of which, c c, is measured on the base line ; to effect this, 1 draw lines from
c c to the point of sight a; and to determine how large the square would appear in
perspective from c c, I have made dotted lines to b b, the points of distance: the