contrast;
while hard negatives are best over-exposed and quickly developed.

The plate is first placed in water or rinsed under a gentle stream from
the tap till all greasiness has disappeared, it is then placed in a flat
dish, and the developer applied. Should it be found that some parts of
the picture are denser printed than should be by the ribbon acting more
strongly on some particular part--this is often the case if the negative
has been thinner in some parts than others, through uneven coating of the
plate--the picture need not be discarded as a failure, for I will explain
to you later on how to overcome this difficulty.

Fix the plate in hypo--the fixing takes place very quickly--then examine
the picture for the faults above described; if they are found, wash the
plate under the tap gently, and bring into operation a camel's hair brush
and a weak solution of cyanide of potassium. Apply the brush to the
over-printed parts, taking care not to work on the places that are not
too dense. Do not be afraid to use plenty of washing while this is being
done; let it be, as it were, a touch of the brush and then a dash of
water, and you will soon reduce the over-printed parts. It only requires
a little care in applying the brush.

After this wash well, and should it be deemed necessary to tone to a
black tone, use a weak solution of bichloride of platinum and chloride of
gold, or a very weak solution of iridium, in equal quantities, allowing
the picture to lie in the solution till the color has changed right
through to the back of the glass. Should a warm pinkish tone be desired,
I tone with weak solutions of ferri cyanide of potassium, nitrate of
uranium, and chloride of gold in about equal quantities.

After toning, wash well and dry; they dry quickly. Varnish with Soehnee
crystal varnish, then mount with covering glasses, and mark. Bind round
the edges with paper and very stiff gum, and the picture is complete.

The making of a really good transparency is by no means an easy or
pleasant task with a wet collodion plate, but with these dry plates an
amateur can, with a little practice, produce comfortably slides quite
equal to those procurable from professional makers.

* * * * *

THE HONIGMANN FIRELESS ENGINE.

The invention of a self propelling engine, capable of working without
fuel economically and for a considerable time, has often been attempted,
and was, perhaps, never