as it were, and not brought out by that length of exposure which
suffices for the former. Hence, statuary, monuments, and all objects
of like character, were remarkably well delineated by the original
process of Daguerre; the plate being coated with iodine alone.
An excess of bromine, to a certain degree, has the opposite effect;
the white portions of the impression appearing of a dull, leaden hue,
while those which should be black, or dark, appear quite light.
This being the case, I conclude there must be a point between the two
extremes where light and dark objects will be in photogenic equilibrium.
The great object, therefore, is to maintain, as nearly as possible,
a perfect balance between the two elements entering into union
to form the sensitive coating of the plate, in order that the lights
and shades be truly and faithfully represented, and that all objects,
whether light or dark, be made to appear so far conformable to nature,
as is consistent with the difference in the photogenic energy
of the different colored rays of light. It is this nicely-balanced
combination which ensures, in the highest degree, a union of the essential
qualities of a fine Daguerreotype, viz., clearness and strength,
with softness and purity of tone.

"So far as I know, it is the universal practice of operators
to judge of the proportion of iodine and bromine in coating
the plate, by two standards of color the one fixed upon for
the iodine, the other for the additional coating of bromine.
Now I maintain that these alone form a very fallacious standard.
first, because the color appears to the eye either lighter
or darker, according as there is more or less light by which we
inspect the coating; and secondly, because if it occur that we
are deceived in obtaining the exact tint for the first coating,
we are worse misled in obtaining the second, for if the iodine