to one tenth.

Wolcott's American Mixture.--Van Loan Quick.--This mixture was first
formed and used by T. Wolcott & Johnson and gained great celebrity for
its productions. I have now a bottle hermetically sealed that contains
about a half ounce of this mixture prepared in 1841 by John Johnson,
now a resident of this city, and the former partner of Mr. Wolcott.
The preparation of this mixture, as furnished by Mr. Johnson himself,
is given as follows:

"One part of bromine, eight parts of nitric acid,
sixteen parts of muriatic acid, water one hundred parts.
This mixture should be allowed to stand for several days;
it improves by age.

"Use.--A few drops say, 6 to 12, of this mixture, should be put
into about 6 or 8 ounces of water; it will require frequent
replenishing by the addition of a few more drops. The plate should
be coated over the dry iodine to a red just bordering on a slate.
and then exposed to the mixture only sufficiently long to change the color.
If this is not done in less than six seconds it is not strong enough.
Re-coat over the iodine full one fourth as long as first coating."

This exceedingly volatile compound is difficult to control
from its instability; it is but little used. The impressions
successfully produced by this mixture are very brilliant,
and possess a pleasing peculiarity.


DRY SENSITIVES.