urnal_ of the
Photographic Society, appears to me the best adapted. It consists of a
modification of the old parallel ruler arrangement on which the camera is
placed; but one of the sides has an adjustment, so that within certain
limits any degree of convergence is attainable. Now in the case of the
pictures alluded to by MR. H. WILKINSON in Vol. viii., p. 181., it is
probable they were taken by a camera placed in two positions parallel to
one another, and it is quite clear that only a _portion_ of the two
pictures could have been really stereoscopic. It is perfectly true that two
indifferent negatives will often combine and form one good stereoscopic
positive, but this is in consequence of one possessing that in which the
other is deficient; and at any rate two _good_ pictures will have a
_better_ effect; consequently, it is better that the two views should
contain exactly the same _range_ of vision.

GEO. SHADBOLT.

_Protonitrate of Iron_.--"Being in the habit of using protonitrate of iron
for developing collodion pictures, the following method of preparing that
solution suggested itself to me, which appears to possess great
advantages:--

Water 1 oz.
Protosulphate of iron 14 grs.
Nitrate of potash 10 grs.
Acetic acid 1/2 drm.
Nitric acid 2 drops.

In this mixture nitrate of potash is employed to convert the sulphate of
iron into nitrate in place of nitrate of baryta in Dr. Diamond's formula,
or nitrate of lead as recommended by Mr. Sisson; the advantage being that
no filtering is required, as the sulphate of potash (produced by the double
decomposition) is soluble in water, and does not interfere with the
developing qualities of the solution.

"The above gives the bright deposit of silver so much admired in Dr.
Diamond's pictures, and will be found to answer equally well either for
positives or negatives. If the nitric acid be omitted, we obtain the
effects of protonitrate of iron prepared in the usual way.--JOHN SPILLER."

(From the _Photographic Journal_.)

_Photographs in natural Colours_.--As "N. & Q." numbers among its
correspondents many residents in the United States, I hope you will permit
me to inquire through its columns whether there is really any foundation
for the very startling announcement, in Professor Hunt's _Photography_, of
Mr. Hill of New York having "obtained more than fifty pictures from nature
in all the bea