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there is a precipitate of sufficient density to cloud the solution, and on which stirring has no effect, allow it to settle for several minutes. When this is done pour off the clear or very slightly clouded solution into another vessel, leaving the precipitate behind. The solutions A and B may now be mixed together either in the silvering dish or mixing vessel, therefore gradually add B to A, stirring well all the time.

With Martin’s process the time occupied with cold solutions seldom takes more than fifteen minutes, and in summer often much less. In fact, I have often effected the entire process, from cleaning to polishing, in less than half-an-hour.

DR. HENRY DRAPER’S FORMULA FOR SILVERING.

Solution B.—Dissolve 560 grains of Rochelle salt in 2 or 3 ounces of water and filter.

Solution A.—Dissolve 800 grains of nitrate of silver in 4 ounces of water; take an ounce of strong ammonia of commerce, and add the nitrate solution to it until' a brown precipitate remains undissolved, then add more ammonia and again some nitrate of silver solution. This alternate addition is to be carefully continued until the silver solution is exhausted, when some of the brown precipitate should remain in suspension. The mixture then contains an undissolved excess of oxide of silver. Filter. Just before using, mix with the Rochelle salt solution, and add water enough to make 22 ounces.

A modification of this process has lately been tried with a fair amount of success In its employment the same chemicals are required, but in a different proportion ; it is as follows :—

A. — Dissolve 2 scruples of nitrate of silver in 5 ounces of water and ammoniate, leaving an excess of silver. To this solution add B :— 1 dram of Rochelle salt in 5 ounces of water, and the deposition of silver will soon commence. Both solutions may be filtered, or allowed to drain through a little cotton wool lightly stuffed into the neck of a funnel.

THE SUGAR OF MILK PROCESS FOR SILVERING.

The chief difference between this formula and that described at length consists in the substitution of sugar of milk for the sugar candy.

A.—Dissolve 2 drams of nitrate of silver, drams of pure potash; and B:—2 drams of sugar of milk, in equal amounts of distilled water. Pour two-thirds of the solution of silver into the mixing vessel, and add liquor ammonias until the precipitate first formed is just re-dissolved; now add all the solution of potash, and re-dissolve the precipitate. Directly the solution becomes clear add the remaining silver, drop by drop, until a slight precipitate is formed, which will not dissolve, even

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