ing a
room dark by _degrees_, and holding up some object against the light as
it _diminishes_, until it is quite dark.

The light of the sun always reflects a shadow _equal_ to the object
which it projects on a parallel plane. The sun being larger than the
body illumined, throws a shadow less than that body. On the contrary,
the light of a candle, being less than the object reflected, produces
the contrary effect, the shadow _increasing_ as it retires, not in
parallels, but in _rays_, thrown by the light.

The figure and shape of a shadow is strictly defined by the form of the
object producing it; as light occasions the existence of shadow. An
excellent and well-turned remark is made by some writer on the subject,
who says, 'It must be observed, that there are _two_ points to be made
use of: one of them, the foot of the light, which is always taken on the
plane the object is placed upon; the other, the luminous body, the rule
being common to the sun, torch, &c. with this difference, that the sun's
shadow is projected in parallels, and that of the torch in _rays_, from
the centre, as before mentioned. But as all objects on earth are so
small in comparison of the sun, the diminution of their shadows is
imperceptible to the eye, which sees them all _equal_, neither broader
nor narrower than the object that forms them. On this account, all the
shadows made by the sun are made in parallels.'

'To find the shadow of any object whatever opposed to the sun, a line
must be drawn from the top of the luminary, perpendicular to the plane
where the foot of the luminary is to be taken; and from this, an occult
line, to be drawn through one of the angles of the plane of the object;
and another, from the sun to the same angle. The intersection of the two
lines will express how far the shadow is to go. All the other lines must
be drawn parallel hereto.'

The next thing to be considered is, an _appropriate_ effect of light or
shadow, to be given to the scene, or object, treated.

Calmness and serenity are the result of _horizontal_ lights, or shadows;
while the contrary is the effect of oblique, or abrupt and irregular;
such as are seen in the stormy effects of Salvator Rosa, &c.

The sky and clouds are often resorted to for _effect_, when the
landscape does not admit of sufficient. Again, less imposition thrown
into the sky, will repose the landscape, when it happens to be invested
with sufficient interest of itself.

Extending