lliancy.

Can you inform me whether portraits can be taken _for sale_, by the
collodion process, without infringing upon the patents?

CHAS. WHITWORTH.

Henrietta St., Birmingham.

_Proportions of Chlorides and Silver._--I trust you will allow me space in
your valuable work for some remarks in reference to an important
photographic query, viz. What are the proportions of chlorides and silver
uniformly suited to give the best positive pictures?

I am led to propose this subject for the consideration of practical
photographists, and, if possible, that amateurs may arrive at something
like a rule to guide them in printing positives that will please.

The necessity of these remarks, to me at least, appear very evident from
the wide space which stands between the proportions proposed by various
operators. MR. LYTE, "N. & Q.," Vol. ix., p. 158., says 42 grains of
chloride and 100 grains of silver to 1 oz. of water. MR. POLLOCK, "N. &Q.,"
Vol. vii., p. 588., says 20 grains chloride, and 90 grains of silver to the
ounce. MR. HOCKIN has 10 grains chloride, silver 60. MR. DELAMOTTE, for
albumenized paper, chloride 60 grains, silver 120. MR. THORNTHWAITE begins
as low as chloride 1/2 grain, and silver 30 grains; and lastly, amidst a long
range of proportions, from 1 grain of chloride to the ounce, and silver 20
grains to the ounce, DR. DIAMOND, a great authority in photography, assures
all that the best results can be obtained by using of chloride 5 grains to
the ounce, and of silver 40 grains to the ounce. If so, let the
photographic world know that the latter proportions are sufficient, and the
others needless, wasteful, and expensive without cause. I trust you agree
with me in thinking that it would be of use to a large number of beginners
to have the proportions best suited for printing positives defined as near
as possible, and not be left to guess at proportions varying from 1/2 grain
to 60 grains, and from 20 to 120. I have written hurriedly, and hope you
will see the object I aim at.

AMATEUR.

{359}

_Photographic Copies of Rembrandt._--The extreme rarity and great pecuniary
value of many of Rembrandt's finest etchings are doubtless well known to
many of our readers, as being such as to put these master-pieces of art
beyond the reach of ordinary purchasers. This series of works, calculated
beyond all others of their kind to delight the possessor, will however,
thanks to photography, soon be obtainable by all adm