was in type, MR. SISSON has written to say, that he has
been informed that the use of nitrate of lead has already been
recommended by MR. W. BROWN. MR. SISSON was not aware of that fact, but
is unwilling to appear in any way to appropriate to himself the
suggestion of another.--ED.]

_Photographic Tent._--Can any of your readers inform me how, or where, to
procure an _effective tent_ for photographic operations out of doors? All
those I have yet seen are sadly wanting in the two great
essentials--_portability_ and _cheapness_. If any one could suggest the
means for supplying the desiderata, it would prove in the coming season a
boon to photographers at large, and confer a favour on

M. F. M.

_Mr. Wilkinson's simple mode of levelling Cameras._--The following
ingenious suggestion appears in the 3rd Number of the _Journal of the
Photographic Society_, and deserves to be widely circulated. "My plan is to
place a T-square on the bottom of the camera, and draw one perpendicular
line on each side (exactly opposite to each other), either with paint or
pencil; or the ends of the camera itself will do if perpendicular to the
base. Then, having two musket bullets attached to a silk thread, simply
hang them over the camera, and everything required will be attained much
quicker by these plumb-lines, and with accuracy equal to the spirit-levels.
The advantage of the simple contrivance of two bullets suspended by threads
is, that when the thread is laid across the camera, it is at once seen
whether the thread touches all the way down both sides; if not, one or
other side of the camera is raised, until the thread lies close on each
side: this gives the level crossways. The other perpendicular of the line
is then sought for, and the back or front of the camera raised or lowered,
until the thread cuts the line drawn below. Here then we have the most
perfect line that can be obtained, at the expense of two bullets and a bit
of silk, answering every purpose of the best spirit-level, and applied in
one-half the time. It has since occurred to me, that as we sometimes
require to measure the distance for stereoscopic pictures, this thread
ought to be about three feet long; and we might as well make three knots,
and then we should have the measure of a three-feet rule always with us. It
has also occurred to me, that in taking portraits you sometimes require to
have a measure of time; and by a little modification we have here t