114 
PHOTOGRAPHICAL SECTION. 
February 20th, 1867. 
Dr. J. P. Joule, F.R.S., &c., Vice-President of the Section, 
in the Chair. 
“ On the Reversed Action of Light in Photography/* by 
Joseph Sidebotham, Esq. 
Those who have for many years been engaged in photo- 
graphic pursuits, either as amateurs or professionals, have 
(especially when trying some new process) met occasionally 
with very curious results — failures as photographic pic- 
tures — but of the greatest value as remarkable results of 
the effects of light. These were probably much more fre- 
quent in the early days of photography, when we were 
dependent in a great measure on our own manufacture of 
chemicals, even to the preparation of aether* Unfortunately 
but few of these curiosities, as we may call them, have been 
preserved ; in the desire to produce good pictures these have 
been thrown aside, and too often the causes of the strange 
results have not been ascertained. This is the more to be 
regretted as discoveries of great value may be hidden under 
these so called failures. On a former occasion I exhibited 
here a collodion positive, on glass, of a landscape, with the 
natural colours, red, green, and blue, very fairly represented, 
although much duller than in nature. This was an over 
exposed picture, and not noticed particularly until a day or 
two after it was taken, and all my subsequent attempts were 
unsuccessful to obtain another similar picture. 
