worst condition; dirty, scratched, and full of mercury spots,
all of which imperfections are more or less to be encountered.
The mercury spots are to be removed by burning the plate.
To do this hold the plate over the flame of a spirit lamp,
more particularly under the mercury spots, until they,
assume a dull appearance, when the lamp is to be removed,
and the plate allowed to cool, after which it is attached
to the block.

Place the block upon the swivle, and hold it firmly with the left hand;
take a small knot or pellet of cotton, or, if you like it better,
a small piece of canton flannel--wet it with a little diluted nitric acid;
then sift some finely prepared rottenstone--Davie's,* if you can get it--
upon it, and rub it over the plate with a continual circular motion,
till all traces of the dirt and scratches are removed; then wipe off
the rottenstone with a clean piece of cotton, adopting, as before,
a slight circular motion, at the same time wiping the edges of the plate.
Even the back should not be neglected, but throughly cleansed from any
dirt or greasy film it may have received from handling.

* Sold by E. Anthony.

When this is thoroughly accomplished, mix a portion of your tripoli
with the dilute nitric acid, to the consistence of thick cream.
Then take a pellet of cotton and well polish the plate with this mixture,
in the same manner as with the rottenstone. Continue the process till,
on removing the tripoli with a clean pellet, the plate exhibits
a clear, smooth, bright surface, free from all spots, or scratches.
Any remains of the acid on the plate may be entirely removed By
sifting on it a little Drying powder, and then wiping it carefully