not discover how to fix it, the whole subject
was laid aside. Between the years 1814 and
1828, two Frenchmen, M. Daguerre and
M. Niepce, were at work upon the problem.
In 1827 M. Niepce produced before the Royal
Society what he then called heliographs, sun-
pictures, formed and fixed upon glass, copper
plated with silver, and well-polished tin. But,
as he kept the secret of his processes, no
scientific use was made of his discovery.
M. Daguerre, working at the same problem,
succeeded about the same time in fixing
sun-pictures on paper impregnated with nitrate
of silver. M. Daguerre and M. Niepce having
combined their knowledge to increase the
value of their art, the French government
—in the year 1839—acting nobly, as it has often
acted in the interests of science, bought for
the free use of the world the details of the
new discovery. For the full disclosure of their
secrets there was granted to M. Daguerre a
life pension of two hundred and forty pounds
(he died not many months ago), and a pension
of one hundred and sixty pounds to the son
of M. Niepce, with the reversion of one half
to their widows.

Six months before the disclosure of the
processes in France, Mr. Fox Talbot in
England had discovered a process leading to
a like result the fixing of sun-pictures upon
paper. As the English parliament buys little
for science, nothing unfortunately hindered
the patenting of Mr. Talbot's method. That
patent in certain respects very much obstructed
the advance of photography in this country,
and great credit is due to Mr. Talbot for
having recently and voluntarily abandoned
his exclusive rights, and given his process to
the public for all purposes and uses, except
that of the portrait-taker. By so doing he
acted in the spirit of a liberal art born in our
own days, and peculiarly marked with the
character of our own time. It does one good
to think how photographers, even while
exercising the new art for money, have pursued
it with a generous ardour for its own sake,
and emulate each other in the magnanimity
with which they throw their own discoveries
into the common heap, and scorn to check the
progress of their art for any selfish motive.
After the completion of the French discovery
two daguerreotype establishments were
formed in London armed with patent rights,
and their proprietors, Messrs. Claudet and
Beard, do in fact still hold those rights, of
which they have long cheerfully permitted
the infringement. Mr. Beard tried to enforce
them only once, we believe; and M. Claudet,
with distinguished liberality, never.

At first the sitting was a long one, for the
original daguerreotype plate was prepared
only with iodine. We see it stated in the
jury reports of the Great Exhibition, that to
procure daguerreotype portraits, it was then
"required that a person should sit without
moving for twenty-five minutes in a glaring
sunshine." That is a glaring impossibility,
and in fact the statement is wrong. It is
to M. Claudet that the public is indebted
for the greater ease we now enjoy in
photographic sittings, and it is the same gentleman
who informs us that five minutes—not
five-and-twenty—was the time required for
the formation of a good picture on the plates
prepared in the old way.

The discovery of the accelerating process,
by the use of the two chlorides of iodine and
bromine, was at once given to all photographers by
M. Claudet; it having been made public
by him, in England, through the Royal Society,
and in France, through the Académie des
Sciences. By the use of this double application,
plates are made so sensitive that
portraits may be taken in a period varying,
according to the measure of the light, between
a second and a minute. We have said
something about varying the degree of
sensitiveness in the plate according to the weather.
In the account just given of our visit to a
photographic studio, it will be seen that a very
skilful artist (Mr. Mayall) lessens at times the
sensitiveness of the plate, but in this respect
the practice is not uniform. In illustration
of the extreme sensitiveness that can be
communicated to the prepared plate, reference
has often been made to an experiment
performed at a meeting of the Royal Society, the
account of which we quote from Dr. Lardner.
"A printed paper was fastened upon the face
of a wheel, which was put in revolution with
such rapidity that the characters on the paper
ceased to be visible. The camera, with the
prepared photographic surface, being placed
opposite the wheel and properly adjusted, the
room was darkened. The room and wheel
were then illuminated, for an instant, by a
strong spark taken from the conductor of a
powerful electric machine. This
instantaneous appearance of the wheel before the
camera was sufficient to produce a perfect
picture." In reading of this experiment we
are not to direct our attention to the sensitiveness
of the plate so much as to the power of
the light. Such a spark as was taken for the
purpose produced an instantaneous light,
greatly surpassing in intensity the ordinary
sunlight used by the photographers. M. Claudet,
in reply to our questions about the adjustment
of the sensitiveness of his plates, replied
simply, "I always try to make my plates as
sensitive as possible." A walk through his
gallery satisfied us that if, by so doing, he
increases the demand on his dexterity in
sunny weather, the demand is met. His results
fully justify his practice.

We may say the same for Mr. Mayall, the
photographer whose operations led us into
the preceding digression. From the dark
cupboard, cleared by a strong up draught of
escaping fumes, we brought the prepared plate
in its frame, carefully excluded from the
light by a protecting slide. The frame was
made to fit into the camera, but before placing
it, the final adjustment of the sitters had to