ut, as with plaster, the surface of the paste
dries very quickly, and this inconvenience (which amounts to nothing in
pieces that are to be polished) is very great in pieces that carry
ornaments in relief, since the finishing of these is much more difficult,
the hardened paste works badly, and frequently flakes off. In order to
remedy this inconvenience, it suffices to dust the places to be preserved
with powdered dry paste.--_Revue Industrielle._

* * * * *

PHOTO-TRICYCLE APPARATUS.

[Illustration: A PHOTO-TRICYCLE APPARATUS.]

This consists of a portable folding camera, with screw focusing
arrangement, swing back, and an adapter frame placed in the position of
the focus screen, allowing the dark slide to be inserted so as to give the
horizontal or vertical position to the dry plate when in the camera. To
the front and base-board a brass swiveled side bar, made collapsible by
means of a center slot, is attached by hinges, and this renders the camera
rigid when open or secure when closed. The base-board is supported on a
brass plate within which is inserted a ball-and-socket (or universal joint
in a new form), permitting the camera to be tilted to any necessary angle,
and fixed in such position at will. The whole apparatus is mounted upon a
brass telescopic draw-stand, which, by means of clamps, is attached to the
steering handle or other convenient part of the tricycle, preferably the
form made by Messrs. Rudge & Co., of Coventry, represented in the
cut.--_Photo. News._

* * * * *

A PHOTO PRINTING LIGHT.

[Illustration]

A printing frame is placed in the carrier, and exposed to the light of a
gas burner kept at a fixed distance, behind which is a spherical
reflector. The same frame may be used for other purposes.-_Photographic
News._

* * * * *

A NEW ACTINOMETER.

A selenium actinometer has been described in the _Comptes Rendus_ in a
communication from M. Morize, of Rio de Janeiro. The instrument is used to
measure the actinic power of sunlight when the sun is at various
altitudes; but the same principle is applicable to other light sources.
The sensitive part of the apparatus consists of a cylinder formed of 38
disks of copper, isolated from each other by as many disks of mica. The
latter being of smaller diameter than the copper disks, the annular spaces
between the two are filled with