Fine paper well sized with an insoluble size and coated with a sensitive
emulsion is, we believe, the very best material to use in the roller slide;
and such a paper might be made in long lengths at a very low price, a
coating machine similar to that constructed for use in making carbon tissue
being employed. We have used such paper with success, and hope that some
manufacturer will introduce it into commerce before long. But the question
suggests itself, how are the paper negatives to be rendered transparent,
and how is the grain of the paper to be obliterated? Simply by pressure, as
extremely heavy rolling will render such paper almost as transparent as
glass, a fact abundantly demonstrated by Mr. Woodbury in his experiments on
the Photo-Filigrane process, and confirmed by some trials which we have
made.

It must be confessed that roller slide experiments which we have made with
sensitive films supported on gelatine sheets, or on such composite sheets
as the alternate rubber and collodion pellicle of Mr. Warnerke, have been
hardly satisfactory--possibly, however, from our own want of skill; while
no form of the Calotype process which we have tried has proved so
satisfactory as gelatino-bromide paper.--_Photo. News_.

* * * * *

INSTANTANEOUS PHOTO SHUTTER.

M. Audra, in the name of M. Braun, of Angouleme, has presented to the Photo
Society of France a new instantaneous shutter. The shutter is formed by a
revolving metallic disk out of which a segment has been taken. This disk is
placed in the center of the diaphragms, in order to obtain the greatest
rapidity combined with the least possible distance to travel. On the axis
to which this circular disk is fixed is a small wheel, to which is attached
a piece of string, and when the disk is turned round for the exposure the
string is wound round the wheel. If the string be pulled, naturally the
disk will revolve back to its former position so much the more quickly the
more violently the string is pulled. M. Braun has replaced the hand by a
steel spring attached to the drum of the lens (Fig. 2) By shortening or
lengthening the string, more or less rapid exposures may be obtained.

[Illustration: AAA, lens; B, aperture of lens; C, metallic disk; D,
wheel on the axis; E, cord or string; EEEE, knots in string; G, steel
spring; H, catch; K, socket for catch.]

* * * * *

SULPHUROUS ACID.--EASY M