152 
PROCEEDINGS OF THE SOCIETY. 
production of photomicrographs had hitherto been found at about 1000 
diameters, and it should not be overlooked that differences in the photo- 
graphic manipulations would very largely influence the results obtained 
by different workers. He thought that many workers had been rather 
betrayed by the reducing power of some of the more recent developing 
agents, such as hydroquinone, and, instead of aiming at the reproduction, 
as far as possible, of the images seen in the Microscope, they had aimed 
at producing photomicrographs of the greatest possible strength of 
contrast, and thus exaggerated effects of black and white had become the 
order of the day. Those who had not the facility of producing photo- 
micrographs were thus apt to think their own manipulation with the 
Microscope must be defective, because they found it impossible to see in 
the Microscope images so strong and definite as those shown in the 
recent photomicrographs. 
Mr. E. M. Nelson said the subject was one of importance in con- 
nection with matters which had occupied much of his attention. As 
regarded the 1000 diameter limit mentioned by Mr. Mayall, he thought 
he had been able to exceed that, his experience leading him to say 
that sharpness could be obtained up to 20 times the initial magnify- 
ing power of the lens. He had produced good photographs direct 
from the Microscope up to X 1500, and recently showed one un- 
touched and undoctored x 1650. In most cases, however, x 1000 
would be found a useful limit ; and he might add that he had taken 
sharp pictures with a 1 in. objective exceeding 20 times the initial 
power of the lens. With regard to the hydroquinone developer, he 
thought it would not give more contrast than was obtained in other 
ways ; if they had a feeble image on the screen they would only get 
a feeble photograph from it, and with high powers he had never been able 
to get in this way much more than he could see. But with lower 
powers they could undoubtedly get very strong contrasts, and could 
sharpen up a picture with hydroquinone, using lenses up to 1/4 in. dry, 
though it could not be done with an oil-immersion. With a dry 1/4 in., 
or with a 1 in. lens, they could under-expose and then get a perfectly 
black and white “ chalky ” picture, as mentioned by Mr. Mayall. As 
regarded enlargement, it was a thing he was utterly opposed to, and he 
thought that all such prints ought to be marked as such, on front and 
back too, if necessary, to prevent any one being deceived by them. In- 
tensification should be regarded much in the same way ; the picture 
shown ought to be the same as the image seen. He did not believe in 
effects produced by doctoring processes, either carried out by chemicals 
or by projection with a lens. These were purely mechanical processes, 
aud as useless for scientific purposes as if drawn with a brush upon 
the screen. 
The Chairman inquired if they could tell whether the photograph 
before them was an enlargement, or whether it had been taken direct ? 
Mr. Nelson said it was easy to say it was an enlargement, but the 
method employed in its production could not be determined by inspec- 
tion. The chief use of enlargement was to convert a poor, weak picture 
into a bold, sharp one. 
The Chairman remarked that people who were dissatisfied with a 
photograph were accustomed to be told that the sun could not lie ; but 
