544 
PROCEEDINGS OF THE SOCIETY. 
substantially-made camera, or movable screen, using such precautions as 
he could devise to give the whole apparatus the greatest possible steadi- 
ness. Chevalier, Hartnack, Nachet, and other opticians, including 
Zeiss, who had devised photomicrographic apparatus, had never, so far 
as he knew, attempted to plan a Microscope specially for the work ; they 
had all adapted some form of camera to the ordinary Microscopes 
constructed by them. Mr. Pringle had, however, made a new departure. 
H aving devoted much attention to the photographic processes, he became 
interested in photomicrography, and in his recently published volume 
on that subject, he frankly acknowledged that he was indebted to Mr. 
Nelson for all his best experience in the use of the Microscope ; he was, 
therefore, familiar with Mr. Nelson’s apparatus and his methods of work. 
With the experience thus gained, he considered it essential to have 
sundry modifications made in the Microscope itself with a view to 
attaining greater general stability, especially as the instrument was 
intended principally for high-class work, and no expense was to be spared 
to make it as efficient as possible. He explained his plans to Messrs. 
Swift, giving them general instructions to produce the best mechanism 
they could make. The result was the apparatus exhibited at the 
meeting. Of the photographic arrangement — the extensible camera and 
the oxyhydrogen lamp — little need be said beyond noting that it seemed 
very well and conveniently devised. He should himself have preferred 
a solid wood box-camera made in sections like Mr. Nelson’s; but that 
was by no means a vital point. He had no doubt that with an extensible 
bellows camera quite as good work could be done as with a box-camera ; 
the preference, then, was a matter of individual choice — the essential 
matter was that the apparatus should be accurately made, and as free as 
possible from vibration. With a solid wood box-camera made in 
sections, weights could be conveniently applied to stop vibration at the 
end where the sensitive plate was placed ; in the bellows arrangement 
clamp-screws were relied upon — in either way no appreciable vibration 
need occur. The oxyhydrogen lamp required a great number of 
adjustments to be made readily ; the lime cylinder had to be raised, or 
lowered, or turned, or it had to be brought nearer to or slid further 
from the Microscope ; for effecting these movements rapidly and 
accurately substantial mechanism was applied. 
As to the Microscope, he supposed that Mr. Pringle had instructed 
Messrs. Swift to provide a substantial extra support at the eye-piece end 
to insure steadiness when the instrument was in the horizontal position, 
and had lett all the other details of the construction to be carried out 
by them on their own plans. But that involved a new departure, for 
the addition of the support at the eye-piece end was a point essentially 
novel, and as it gave additional stability, he thought it would probably 
be adopted, with more or less modification, as an adjunct to all the best 
photomicrographic arrangements henceforth, for its merits were 
unquestionable ; moreover, the plan was easily applicable to any form 
of Microscope. Messrs. Swift had adopted the “Jackson” form of limb, 
modifying the usual modern construction by making it long enough to 
support the whole length of the body-tube, both when high or low 
powers were in use, thus reverting in principle to Jackson’s original 
design, which had been rather neglected in recent times. The Jackson 
form of Microscope, as usually made by the American and English 
