n an open
vessel in a warm place for some weeks, _e.g._ till, when a positive is
placed in it, left for a short time, and then washed with water, it shows
clean and not mottled in the light. The solution may be kept always
exposed, and much improves by this: if _much_ used, it should be
replenished with a simple solution of hypo. three ounces or two ounces to
the pint; if little used, it may be filled up as much as evaporates with
pure water.

The positive is left in this solution till the required tint is obtained,
when it is to be placed in plain hypo. two ounces to the pint, and in about
a quarter of an hour transferred to a basin of pure water, and well washed
in several waters. The other detail of MR. POLLOCK's process is so
admirably and clearly given, and so like that I pursue, that I will not
trouble your columns with it again.

The after-bath of pure hypo. is not absolutely necessary; and where it is
desired to obtain fine olive, and dark sepia, and black tints, a better
tone results from washing well, long, and frequently, with water alone.

This bath also gives very rich tints with paper, prepared without albumen:
viz.--

Chloride of ammonium 5 grs.
Water 1 oz.

Lay the paper on this, and then hang it up to dry, and excite with
ammonio-nitrate containing seventy grains of nitrate of silver to one ounce
of water. Should the above solution not give the requisite tints soon after
being made, add more chloride of silver; but bear in mind that the solution
will then soon become saturated when setting positives, and when this
occurs it must be rectified by the addition of a small portion of fresh
hypo. alone.

F. MAXWELL LYTE.

P.S.--I may add that I have only lately tried the addition of the iodide of
potassium to my setting liquid, and so must qualify my recommendation of it
by saying so.

Florian, Torquay.

_Stereoscopic Angles._--I am obliged to MESSRS. SHADBOLT and WILKINSON for
the information given in reply to my Queries (Vol. vii., p. 505.) My mode
of operation is precisely that of MR. WILKINSON: "I obtain all the
information I can from every source; then try, and judge for myself." Hence
the present letter.

I regret to be obliged to differ from MR. SHADBOLT, but there is a point in
his communication which appears to me to arise from a misconception of the
stereoscopic problem. He says (p. 557.), "for _distant_ views there is in
nature scarcely any _stereoscopic_