printing on a great scale, as compared with woodcut, lithograph, &c.; in
which must be included the cost of the skilled workman which will be saved
by this method?

HUGH BLACKBURN.

[When we add that the work referred to is an edition of _The History of
Little Downey_, that the prints in it are executed by a lady, and
printed at home by the photographic process, and that a limited number
of copies may be had on application to Messrs. {629} Constable and Co.
of Edinburgh, the sale being for the benefit of the Glasgow Ragged
School, we have no doubt many of our readers will be glad to secure
copies, and help to forward the good work which its publication is
intended to promote.]

[Footnote 5: This method was suggested to me by Professor Maconochie, who
indeed prepared the glass on which the mice were etched.]

_Collodion Negatives._--Allow me to communicate a sure and simple way of
darkening collodion positives for printing. It was shown to me by a friend
of mine; and not having seen it in your "N. & Q.," I have undertaken to lay
it before your readers, hoping that it may be found useful to many
beginners.

After having developed your picture, as a positive, with protosulphate of
iron and nitric acid, wash it well from the developing fluid, and keep it
on one end that all the water may drop from the plate. Then take three
parts of a concentrated solution of gallic acid, and one part of a nitrate
of silver solution, 60 grains to the ounce of water; mix together, and pour
on the plate. The picture will gradually begin to blacken; and after half
an hour or more, you will obtain a sufficient density for printing a
positive on paper.

Every one who will take the trouble to try it will be sure to succeed. Of
all the ways to blackening a picture for printing I have tried, not
excepting Professor Maconochie's method with chloride of gold and muriate
of ammonia, the surest I find is the one which I have laid before you. Just
try it, and you will be glad with the result.

F. M. (a Maltese.)

Malta, Valetta.

* * * * *

Replies to Minor Queries.

"_London Labour and the London Poor_" (Vol. viii., p. 527.).--I beg to
inform MR. GANTILLON that the above work is discontinued. The parts
entitled "Those that will work" and "Those that cannot work" have been
completed, and form a valuable book; but the discontinuance of the third
part is no loss at all, for i