wherever they liked the lines to go, provided only
they left just perspective enough to please the public.

xiii. In modern days, I doubt if any artist among us, except David
Roberts, knows so much perspective as would enable him to draw a Gothic
arch to scale at a given angle and distance. Turner, though he was
professor of perspective to the Royal Academy, did not know what he
professed, and never, as far as I remember, drew a single building in
true perspective in his life; he drew them only with as much perspective
as suited him. Prout also knew nothing of perspective, and twisted his
buildings, as Turner did, into whatever shapes he liked. I do not
justify this; and would recommend the student at least to treat
perspective with common civility, but to pay no court to it. The best
way he can learn it, by himself, is by taking a pane of glass, fixed in
a frame, so that it can be set upright before the eye, at the distance
at which the proposed sketch is intended to be seen. Let the eye be
placed at some fixed point, opposite the middle of the pane of glass,
but as high or as low as the student likes; then with a brush at the end
of a stick, and a little body-color that will adhere to the glass, the
lines of the landscape may be traced on the glass, as you see them
through it. When so traced they are all in true perspective. If the
glass be sloped in any direction, the lines are still in true
perspective, only it is perspective calculated for a sloping plane,
while common perspective always supposes the plane of the picture to be
vertical. It is good, in early practice, to accustom yourself to inclose
your subject, before sketching it, with a light frame of wood held
upright before you; it will show you what you may legitimately take into
your picture, and what choice there is between a narrow foreground near
you, and a wide one farther off; also, what height of tree or building
you can properly take in, etc.[B]

xiv. Of figure drawing, nothing is said in the following pages, because
I do not think figures, as chief subjects, can be drawn to any good
purpose by an amateur. As accessaries in landscape, they are just to be
drawn on the same principles as anything else.

xv. Lastly: If any of the directions given subsequently to the student
should be found obscure by him, or if at any stage of the recommended
practice he find himself in difficulties which I have not enough
provided against, he may apply by letter to Mr