inims of
chloroform, dropping in the latter, which will fall to the bottom, but is
readily dissolved on shaking the mixture for a few minutes.

To two drachms of the same alcohol add the iodizing material preferred, and
mix with the other ingredients.

The above will be found to flow very evenly smoothly over the plate; is
tough, intense, and _structureless_ in appearance. I have not yet
determined what is the best iodizing mixture, but at present I prefer
iodide of potassium _alone_, if pure, and twenty grains to the ounce of
alcohol is the proportion I generally adopt; thus having five grains in
each ounce of collodion.

Lastly, as regards the soluble cotton, I cannot find any better material
than that produced according to the formula published by Mr. Hadow, in the
March Number of the _Photographic Journal_, thus: "Take of nit. potash,
five parts; sulphuric acid, ten parts; water, one part; _all by weight_.
Add the water to the nitrate of potash, and then the acid, and immediately
immerse as much cotton wool as can be thoroughly saturated by the mixture,
leaving it in for _at least_ ten minutes, and wash with a great abundance
of water. The object of adding the cotton immediately that the acid has
been mixed with the nitrate of potash, is to expose it to the action of the
chemicals while they are at a temperature of from 120deg to 130deg. For
farther particulars on this head, I must refer to Mr. Hadow's paper.

GEO. SHADBOLT.

[This application is not a novelty to us: DR. DIAMOND has for some time
added a small portion of his amber varnish (which is prepared from
chloroform) to his collodion, and with satisfactory results. It is a
pity that so admirable a varnish is not to be procured at the
generality of photographic warehouses. We have never yet been able to
procure any which will bear comparison with some which DR. DIAMOND was
good enough to prepare for us.--ED. "N. & Q."]

_Printing Positives._--I will venture to assure AMATEUR that,--if he will
follow DR. DIAMOND'S formula for albumenizing Canson paper, either positive
or negative, viz.,

Chloride of sodium (salt) 5 grs.
Chloride of ammonium 5 grs.
Water 1 oz.
Albumen, or the white of one egg, which
is near enough for the purpose 1 oz.

and will excite this paper by floating it for about two minutes on a
solution of nitrate