The microscope is
signed on the limb Swift & Son,
University St, London W.C. with the
Swift bird trade mark. The firm had this name and
address during the years 1877-1881. This microscope
is based on a design first introduced by George
Wale in 1879 with his "New
Working Microscope", which featured a
limb allowing a novel way to incline the
microscope. Evidently, Swift thought this was a
useful feature. He first used this with a
microscope called the Improved Wale's
American Microscope and later he applied this
feature to some more advanced models. The
microscope shown here is constructed in brass with
bright lacquered and black oxidized surface
finishes. As opposed to the standard version of this model, it has additional features that arrange
it into a polarizing (mineral/petrological) microscope. The storage case now with the microscope is a replacement.
The standard version of this model is
illustrated and described in The American Monthly
Microscopical Journal, Volume 4, 1883 as
follows:
"Another
ingenious contrivance applied to some of Mr.
Swift's stands is precisely what we have endeavored
to induce our own manufacturers to adopt, but
without success. It is a revolving plate of
diaphragms fitted in the stage-plate. This is shown
in the illustration (fig. 45), of the modification
of the stand first introduced by Mr. George Wale,
made by Messrs. Swift & Son, under the name of
the Improved Wale's American Microscope. The
milled edge of the diaphragm-plate is seen
projecting from the front of the stage-plate. The
device is not new, being in fact, as we are told, a
very old one; but it is none the less good, and
Messrs. Swift & Son apply it to several of
their microscopes.
The design of the
Wale stand, as applied by Mr. Swift, seems to have
been suggested by the radial microscope devised by
Mr. Wenham, while the plan of construction is
copied from the simple and inexpensive stand of Mr.
Wale, which has been so highly commended by Dr. W.
B. Carpenter, and others. At first glance it
appears to be almost identical with the last
mentioned instrument, but it possesses this
peculiarity that the centre of curvature of the
rocker is at the focal point for an object on the
stage. The small milled head beneath the coarse
adjustment is for the fine adjustment, the plan of
which will be described in a future
article.
Unlike the standard version of this model, the microscope shown
on this page has some additional features that
convert it into a polarizing (mineral/petrological)
microscope. Among these features is a sub-stage that is fitted with a
polarizing condenser that can be rotated, a stage with centering adustments that
is capable of full rotation through the optical
axis, and a centering nosepiece onto which
attaches the analyzing prism and objective.
The microscope has
Swift's novel fine adjustment mechanism, which is
described in the Journal of the Royal
Microscopical Society, 1881 as follows:
"The principal
novelty is the fine adjustment (Fig. 43, nearly
full size). A is a brass plate having short
angle-bearings at either end sliding in the grooves
B B and carrying at the lower end a ring into which
the objectives are screwed. A spiral spring C
presses down the plate A. The focussing is by means
of the fine screw worked by the milled head F, the
point of which acts upon the trigger-shaped lever D
(attached to the side), which pushes against the
small metal disk E (mounted on A and rotating on a
pinion to diminish friction) and this lifts up the
slide A against the pressure of the spiral spring
above. The ring carrying the objective is quite
independent of the microscope-body, and should the
slide A be found to work too easily or the reverse,
the bearings can be readily adjusted by the capstan
screw-heads shown at the side.
An improved
application of this fine adjustment has since been
devised, as shown in Fig. 44; the modification
consisting of a wedge-shaped lever worked by the
fine-focussing screw (against a short spiral
spring) and acting on the slide A by means of the
two small revolving disks attached loosely by a
triangular fitting to the pinion at E. By making
the slope of the wedge very acute, and the thread
of the screw very fine, the focussing movement is
rendered unusually delicate. This latter form of
fine adjustment is designed to be applied to more
expensive Microscopes".
The microscope shown
here utilizes the earlier form of the fine
adjustment shown in fig. 43.