osure must be regulated to suit the degree of sensitiveness to red,
which cannot safely be made greater than I have realized with my
chlorophyl process.

* * * * *

DISTORTION FROM EXPANSION OF THE PAPER IN PHOTOGRAPHY.

The effect of the unequal expansion of paper, when wetted, in causing
distortion of the photographic image impressed upon it, has, in the case
of ordinary photographs upon albumenized paper, been well recognized; but
the extent to which such distortion may exist under different treatment
is worthy of some special consideration, particularly with reference to
the method of printing upon gelatinized paper, which has been thought by
some likely to supersede the method now usually employed with albumenized
paper.

When a print upon the ordinary photographic (albumen) paper is wetted,
the fiber expands more in one direction than in the other, so that the
print becomes unequally enlarged, very slightly in one and much more so
in the other way of the paper. When the paper is dried without any strain
being put upon it, the fibers regain very nearly their original
dimensions and position, so that the distortion which has existed in the
wet condition nearly disappears.

If the photograph is cemented, while in the expanded condition, upon a
rigid surface, the distortion then existing is fixed, and rendered
permanent. Such a cementation or method of mounting is that which has
been generally adopted, and the consequence has been that every now and
then complaints have justly been made of the untruthfulness--owing to
this particular distortion--of photographs; productions whose chief merit
has often been asserted to consist in their absolute truthfulness. This
distortion is very manifest when, in a set of portraits, some of the
prints happen to have been made in one direction of the paper, and others
with the long grain the other way. I have known a case where a proof
happened to increase the face in width, and all the other prints
increased it in length. Of course, neither was correct, but the proof had
been accepted and liked, and the remainder of the set had to be reprinted
with the grain of the paper running in the same direction as that in the
first one which had been supplied.

Another evil arising from mounting prints while expanded with moisture
is, that in drying the contraction of the paper pulls round the card into
a curved form and although by rolling this curv