white light besides the prism, of which one of the principal
and most interesting to the Daguerreotypist is by reflection from
colored bodies. If a beam of white light falls upon a white surface,
it is reflected without change; but if it falls upon a red surface,
only the red ray is reflected: so also with yellow and other colors.
The ray which is reflected corresponds with the color of the object.
It is this reflected decomposed light which prevents the beautifully-colored
image we see upon the ground glass in our cameras.

[amdg_2.gif]

A sunbeam may be capable of three divisions--LIGHT, HEAT, and ACTINISM;
the last causes all the chemical changes, and is the acting
power upon surfaces prepared to receive the photographic image.
The accompanying illustration, Fig. 2, will readily bring
to the mind of the reader the relation of these one to another,
and their intensities in the different parts of a decomposed sunbeam.

The various points of the solar spectrum are represented in the order
in which they occur between A, and B, this exhibits the limits of the
Newtonian spectrum, corresponding with Fig. 1. Sir John Herschel and Seebeck
have shown that there exists, beyond the violet, a faint violet light,
or rather a lavender to b, to which gradually becomes colorless;
similarly, red light exists beyond the assigned limits of the red ray to a.
The greatest amount of actinic power is shown at E opposite the violet;
hence this color "exerts" the greatest amount of influence in the formation
of the photographic image.

(Blue paper and blue color have been somewhat extensively used by