Thus the positive process of carbon printing would be
modified in such a manner that the mixtures containing the permanent
pigment should be sensitized with silver bromide in place of potassium
bichromate. In this way impressions could be very rapidly taken of
positive proofs, and enlargements made, which might be developed in hot
water, just as in the ordinary carbon process, and at least we should
have permanent images. Mr. Warnerke's highly interesting experiments
will no doubt open the way to many valuable applications, and will
realize a marked progress in the art of photography.
_Method for Converting Negatives Directly into Positives_.--Captain
Bing, who is employed in the topographic studios of the Ministry of
War, has devised a process for the direct conversion of negatives into
positives. The idea is not a new one; but several experimenters, and
notably the late Thomas Sutton, have pointed out the means of effecting
this conversion; it has never, however, so far as I know, been
introduced into actual practice, as is now the case. The process which
I am about to describe is now worked in the studios of the Topographic
Service. The negative image is developed in the ordinary way, but the
development is carried much further than if it were to be used as an
ordinary negative. After developing and thoroughly washing, the negative
is placed on a black cloth with the collodion side downward, and exposed
to diffuse light for a time, which varies from a few seconds to two or
three minutes, according to the intensity of the plate.
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