PROCEEDINGS OF THE SOCIETY. 
153 
it seemed as if something of the sort could happen through the medium 
of the processes mentioned. 
Mr. Mayall said that when a draughtsman made a drawing of an 
image seen in the Microscope, he adopted some conventional method of 
representing differences of colour, light and shade, &c., and in some 
points his personal equation was an important factor, as evidenced by 
the different renderings that would be given by different draughtsmen. 
Bnt it should not be supposed that by means of photography all these 
difficulties were conquered, and that the photographic interpretation 
could be wholly relied upon for giving uniform results. Photography 
itself might be said to have a considerable range of “ photographic 
equation,” due to the variety in the processes that were available, and 
it was an extremely difficult matter to suggest any one process that 
should be regarded as a standard or guide for general adoption in con- 
nection with Microscopy. It was quite certain that a skilled mani- 
pulator could so direct the processes that almost any point could be 
accentuated in a photograph. As an example, he might mention that 
Mr. Nelson had shown him negatives of a Triceratium in which the 
general contours of a hexagonal “ pit ” were very well shown, but in 
which it was hardly possible to'detect any differentiation at the bottom 
of the pit, though in the Microscope a dotted appearance was seen. A 
new negative was made with much less exposure, and though the general 
contours were not so evident, the dotted appearance in the pits was 
shown. This was clearly an instance that photography had its own 
methods or conventionalities in dealing with particular points — the 
mere reduction of the exposure enabled the sensitive film to pick up 
faint differences in luminousness of closely adjacent parts which had 
previously been blurred together by the over-exposure. He thought the 
importance of having the full data given with every photomicrograph 
would soon be recognized, and that the comparison of results would thus 
become more useful. At present the matter was somewhat chaotic, for it 
frequently happened that the processes employed were so mixed up that 
no proper comparisons could be made. Photomicrographs were pro- 
duced with sunlight, diffused daylight, electric light, oxy-hydrogen 
light, petroleum light, gaslight, &c. ; the negatives were intensified or 
not, or were developed in some special way ; the exposures were timed 
to exhibit this or that point ; the plates were isochromatic or not ; and 
yet the results were dealt with as if the comparisons were being fairly 
made on the same lines. Or, again, enlarged photographs were made 
from many of these photomicrographs by processes which were known 
to completely alter the character of the originals, and these were com- 
pared with each other, or with the various originals, in such a way that 
the whole subject became confused. In twenty years hence, the student 
who should examine the Society’s collection of photographs would be 
sorely puzzled to determine what the present generation of photo- 
micrographers had really been aiming at. 
The Chairman thought the thanks of the Society were due to those 
gentlemen who had favoured them with communications, and who had 
sent exhibits to the meeting. The causes which had operated in preventing 
the attendance of the President and Prof. Bell had no doubt deterred 
many others from being present that evening. He also announced that 
