ied to the last
buff, and it is obvious that three buffs can be employed to adventure;
the two last should not receive any polishing materials. I have
examined a plate that was considered to possess a fine finish, and
similar had produced good impressions; these same plates, when
subjected to a long and light buffing, would present a surface no finer
in appearance to the naked eye; but upon exposure to the solar
radiation, would produce a well-defined image in one fourth less time
than the plate without the extra buffing.

Coating the Plate.--For this purpose our mechanics and artists have
provided a simple apparatus called a coating-box, which is so arranged
as to be perfectly tight, retaining the vapor of the iodine or
accelerators, and at the same time allowing, by means of a slide, the
exposure of the plate to these vapors. They can readily be obtained by
application to any dealer, all of whom can furnish them.

The principal difficulty in coating the plate, is that of preserving
the exact proportion between the quantity of iodine and bromine, or
quick. It is here necessary to say, that hardly any two persons see
alike the same degree of color, so as to be enabled to judge correctly
the exact tint, i. e. what one might describe as light rose red, might
appear to another as bright or cherry red; consequently, the only rule
for the student in Daguerreotype, is to study what appears to him to be
the particular tint or shade required to aid him to produce the desired
result. Practise has proved that but a slight variation in the
chemical coating, of the Daguerreotype plate will very materially
affect the final result.

The operator will proportion the coating of iodine and bromine or
accelerators according to the strength and composition of the latter.

Experience proves that the common impressions, iodized to a rather
light yellow gold tint, and brought by the bromine to a very light,
rose color, have their whites very intense, and their deep shades very
black. It is also known that if you employ a thicker coating of iodine
and apply upon it a proportionate tint of bromine, so as to obtain a
deep rose tint, delineations will be less marked, and the image have a
softer tone. This effect has been obvious to everyone who has
practised the art. Thus I may observe that the light coatings produce
strong contrast of light and shade, and that this contrast grows
gradually less, until in the very heavy coating it alm