66 
GEOLOGICAL SECTION. 
Thursday, April 25th. — In consequence of the illness of Mr. W. 
Sanders, who was to have read a paper, the meeting announced for this 
evening was postponed. 
CHEMICAL AND PHOTOGRAPHIC SECTION. 
Wednesday, May 8th. — Mr. P. J. Worsley, B.A., F.C.S., President 
of the Section, in the chair. 
Mr. John Beattie made a verbal communication entitled "Photo- 
graphic notes." The first had reference to the " touching " or working-up 
of negative pictures, either landscape or portrait, but more especially the 
latter. Many pigments had been tried, and the instrument that gave the 
best result was a very fine soft lead pencil. Indian ink was also used to 
great advantage. In this way, a beautifully stippled negative could be 
obtained, of great softness ; every part could be touched except the highest 
lights. 
The second note was upon the use of glycerine in keeping ordinary wet- 
collodion plates sensitive for several hours. When a period not exceeding 
three hours was sufficient, the bath might be acidulated with nitric acid, 
but by the use of acetic acid the speaker had succeeded in keeping a plate 
sensitive for 10 hours. He believed that the free nitric acid promoted 
too rapid oxidation upon the plate, destroying its sensitiveness. His 
formula was 1 oz. glycerine, 1 oz. water, 1 oz. nitrate of silver, 30-grain 
solution. After incorporating the mixture, and allowing it to stand, it was 
to be filtered, and was ready for use. The plate should be sensitised in 
the usual manner, and this solution poured over it. In developing, there 
was often a difficulty in getting the developer to spread evenly over the 
plate, and he had reverted to the old plan of dipping the plate into the 
developer, with very good results. This process was invaluable for inte- 
riors, which were necessarily exposed for a long time. 
Much had been said and written about the use of gelatin in developers. 
Mr. Beattie was convinced that an excessive quantity was usually recom- 
mended : he was in the habit of using seven grains proto- sulphate of iron 
seven drops of acetic acid, and 1^ dram of a 1§ grain solution of gelatin, 
strengthening the picture with pyrogallic acid and silver. 
The President exhibited a very beautiful set of Frith's photographs of 
Swiss scenery, many of the negatives of which had been evidently worked 
up, as described by Mr. Beattie. He also showed some rough-looking, 
but very effective photographs, printed upon coarse drawing paper. They 
were produced by Mr. Taylor, of Marseilles, according to a process which 
he had invented, termed the shell-lac process — in which shell-lac dissolved 
in borax was used. Mr. Worsley also mentioned that he had seen lately 
in Paris a small camera with fixed lenses, without any focal adjustment, 
which gave with dry plates very good results. The small pictures pro- 
duced by it were readily enlarged. 
