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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points where they intersect the lines drawn to the point of sight, will give the true
size of the other three sides of the square.
Accidental points are so called, because they are not drawn to the point of sight,
or to the point of distance, but appear accidentally on the horizon, according to the
situation of the object; thus e in the drawing before us, is a block of stone lying in
such a position, that though it must of course appear in perspective, it cannot be
drawn either to the point of sight or of distance; its sides must however, like those of
all other objects, terminate in a point in the horizon ; this would in the present case
fall at f, which is therefore the accidental point of this object, j is another block ;
which can only be put in perspective by continuing the horizontal line a long way
out of the picture, to shew where the accidental point is to be found.
As I have briefly, but it is hoped satisfactorily, explained the nature of most of
the points and lines used in perspective drawings, we must proceed to a practical ap-
plication of them. The next plate (XVI.) contains three figures, which you may
vary at pleasure, till you are quite conversant with all the lines and points treated of
in this and the former letter.