in about five minutes. The supernatant fluid is then gently poured off.

This fluid will have the appearance of still containing a considerable
amount of the silver bromide; but if it be kept and filtered it will be
seen that the quantity is really so small that it may be disregarded. We
all know what an alarming quantity of silver seems to be going down the
sink when we wash vessels to which a very small quantity of emulsion is
adhering. If filtering be resorted to the liquid which comes through
will be quite clear. This was somewhat unexpected by me, as, if an
emulsion containing the whole of the gelatine be precipitated into
alcohol in the usual way, the alcohol becomes milky with a substance
which could not, I imagine, be filtered from it.

Two or three ounces of methylated spirit are now added to the vessel
containing the silver bromide, and the latter well mixed with it. This
makes the precipitate "firmer"--if such an expression be allowable--and
this time it will sink to the bottom almost immediately after the
stirring has ceased, and the alcohol may be poured off.

I consider that the bromide in this state is practically free from
soluble salts, but it may be washed with one or two changes of water if
desired.

No. IV. is now gently heated till the gelatine is melted and the
precipitate mixed with it. It must be kept warm for some time, and
shaken vigorously until all granularity has disappeared, This is, of
course, ascertained by placing a drop of the emulsion on a piece of
glass, and examining it. If it be wished to keep the bromide of silver
for future use it may be placed on a piece of muslin stretched in the
drying-box, when it will dry in a very short time; and, although I