This is a fine example of
the classic bar-limb design first introduced by Andrew
Ross in 1843. It incorporates a number of improvements
of the original model.
The accessories are
stored in the lower four drawers of the case (the upper
two drawers are for slides). They consist of four
eyepieces, four Ross objectives with their brass
canisters, substage polarizer, eyepiece analyzer, two
live boxes, glass trough, camera lucida, hand forceps,
stage forceps, stage-mounted bulls-eye condenser,
substage wheel of apertures, substage dark-well holder
with three dark-wells, mechanical eyepiece micrometer,
a large leather box with glass pipettes, another
leather box with a sectioning razor, a small leather
box with a selenite slide, and one with a quarter wave
plate (marked R&J Beck), a simple lower power
substage condenser, and a fine example of Gillett's
condenser, which bears a Ross signature; additionally,
there are some other odds and ends/adapters.
The following was extracted from
Quekett's Practical Treatise on the Use of the
Microscope, third edition, 1855. It is quote from
Andrew Ross's description of the improved form of the
1843 design:
This instrument, first
described by Mr. Ross in the London Physiological
Journal, in 1843, is represented by Plate 1; and as no
language of the author could convey so good an idea of
its construction as that given by Mr. Ross himself, his
own words will here be quoted :
"The mechanical
construction represented in Plate 1, is derived from a
practical acquaintance with the various improvements
made in the microscope for the last twenty years. The
general arrangement, which is properly the province of
the mechanic, has been contrived to obtain the utmost
freedom from tremor, and to afford the greatest
facility in using the various movements, while the
extent, direction, and number of these have been
collected from the experience of the most indefatigable
observers in all the various branches of microscopic
inquiry. Nearly six hundred instruments have been made
on the plan here represented, and as but slight
alteration or addition in detail, has been found
necessary for the accomplishment of all the modes of
microscopic investigation at present employed, the
mechanical structure of the microscope stand may be
considered thus far established
The optical part also has
arrived at such perfection, that points or lines, whose
distance is such that their separation is bordering on
interfering with the physical constitution of light,
can be distinctly separated; thus ensuring a reality in
the appearance of objects, where the minuteness of
their detail approaches the natural limit of
microscopic vision.
A are two uprights,
strengthened by internal buttresses, mounted on a
strong tripod, B, at the upper part, and between the
uprights is an axis upon which the whole of the upper
part of the instrument turns, so as to enable it to
take a horizontal or vertical position, or any
intermediate inclination, such, for instance, as that
shown in the plate. This moveable part is fixed to the
axis near its centre of gravity, and consists of the
stage, D, the parallelopipedon bar and its socket shown
at C, with its arm, which carries the microscope tube,
E, and the mirror, M. The stage, D, has rectangular
movements, one inch in extent, on dovetail slides, and
is moved by a pinion and screw connected with the
milled heads, H I, and it also has the usual appendages
of forceps to hold minute objects, and lens to condense
the light upon them. The parallelepiped bar, together
with the arm and microscope tube, is moved by the
milled heads at G, and a more delicate adjustment of
this optical part is effected by the milled head F. The
other milled head, K, fixes the arm to the
parallelepiped bar. The outline of the structure, as
before observed, has been arranged to obtain, first,
the utmost freedom from tremor, and, secondly, to
afford the greatest facility in using the various
movements.
In experimenting to
obtain the first of these conditions, I suspended the
moveable part of the instrument near the centre of
gravity, and employed the inverted pendulum (an
instrument contrived to indicate otherwise insensible
vibrations) to arrange the form and quantity of
material so as to produce, as nearly as possible, an
equality of vibration throughout the whole instrument;
hence the object upon the stage and the optical part
vibrating equally, no visible vibration is caused. The
arrangement for accomplishing the second condition is,
first, that the whole movements should be as near the
base of the instrument as is consistent with the
greatest proximity among themselves; then the milled
heads at G for moving the parallelepiped bar, and the
fine adjustment for the optical part, should be moved
by the left hand, while the heads H and I, for the
movement of the stage, should be worked by the right
hand. The other milled head, opposite G, is convenient
when the right hand may be unemployed with the stage
movements. The positions of the milled heads, H and I,
are extremely convenient, as the middle finger may be
placed under H, and the fore-finger under I, and the
thumb passed from the one to the other in the most
natural and easy manner. The left hand is also readily
shifted from the milled head at G, to employ the fore
or middle finger to move the screw head F. This head is
connected with a screw and lever, which makes one
revolution of it move the optical part one
three-hundredth of an inch. This arrangement affords an
elastic movement to the end of the tube, as a guard
against injuring the glasses or the object under
examination.
By means of the milled
head at e, the whole stage, D, carrying the object may
be rotated one-third of a revolution (note: the
example presented herein does not incorporate the
milled head e, but instead, the stage can
be rotated by hand) underneath the
object stage, D, is the secondary stage, a a, and b,
which consists of a cylindrical tube, having a rotary
motion by means of the milled head, c, also a
rectangular adjustment which is effected by to screws,
one on front at d, and the other on the left side of
the frame. This tube receives and supports the various
illuminating and polarizing apparatus and other
auxiliaries which are placed underneath the object The
cylindrical tube and its frame are affixed to a
dovetail sliding bar, and can be easily removed for
conveniently attaching the various apparatus. This
sliding bar fits into a second slide, which, by means
of a milled head on the left of the general stage
moving a rack and pinion (not to be seen in the plate),
serves to regulate the distance of the apparatus from
the stage. The condenser of Mr. Gillett, hereafter to
be described, is represented by, as being fitted into
the tube, a."
The following description
of Gillett's condenser was extracted from The
Microscope by J. Hogg, 1859:
Gillett's
Illuminator, or Condenser. The advantages of
employing an achromatic condenser were first pointed
out by Dujardin, since which time an object-glass has
been frequently but inconveniently employed; and more
recently achromatic illuminators have been constructed
by most of our instrument makers. Some years since, Mr.
Gillett was led by observation to appreciate the
importance of controlling not merely the quantity of
light which may be effected by a diaphragm placed
anywhere between the source of light and the object,
but the angle of aperture of the illuminating pencil,
which can be effected only by a diaphragm placed
immediately behind the achromatic illuminating
combination. Such a diaphragm is represented in fig.
42, manufactured by Mr. Ross: it consists of an
achromatic illuminating lens c, which is about equal to
an object-glass of one-quarter of an inch focal length,
having an angular aperture of 80 degress. This lens is
placed on the top of a brass tube, intersecting which,
at an angle of about 25 degrees, is a circular rotating
brass plate a b, provided with a conical diaphragm,
having a series of circular apertures of different
sizes h g, each of which in succession, as the
diaphragm is rotated, proportionally limits the light
transmitted through the illuminating lens. The circular
plate in which the conical diaphragm is fixed is
provided with a spring and catch ef, the latter
indicating when an aperture is central with the
illuminating lens, also the number of the aperture as
marked on the graduated circular plate. Three of these
apertures have central discs, for circularly oblique
illumination, allowing only the passage of a hollow
cone of light to illuminate the object. The illuminator
above described is placed in the secondary stage i i,
which is situated below the general stage of the
microscope, and consists of a cylindrical tube having a
rotatory motion, also a rectangular adjustment, which
is effected by means of two screws I m, one in front,
and the other on the left side of its frame. This tube
receives and supports all the various illuminating and
polarising apparatus, and other auxiliaries which are
placed underneath the object. The tube and its ftame
are affixed to a dovetailed sliding bar k, which can be
easily moved up or down, or taken off for conveniently
attaching the various apparatus. This sliding bar fits
into a second sliding bar, which, by means of a
milled-head screw, moving a rack and pinion, regulates
the distance of the apparatus from the stage.
A later example of a
large Ross No.1 is also represented in this
collection. For other early microscopes made by Andrew Ross and a short history of the Ross firm see:
this