An early and uncommon B&L microscope with screw tube focusing, c. 1875
Likely the firm's first production model
The claw-footed base is
black japanned iron with a spread of 5-3/4 x 5-1/2
inches, and supports the two brass 2-3/4-inch-high
tubular pillars of this instrument. A japanned Lister
limb, 6-1/2 inches long, screws on the trunnion; the
lower 2 inches of the limb form the tailpiece. The
1-9/16-inch single concave mirror is on a
ball-and-socket gimbal.
The stage is fixed to the
limb, is 2-1/2 x 3-1/4 inches, has a 1/2-inch central
aperture, and is fitted for stage clips; beneath the
stage is a revolving disc of diaphragms. The upper end
of the limb is attached to a sprung tube, 3-1/4 x
1-3/16 inches.
The body tube is 7-1/2
inches long and fits into the outer tube; there is a
screw focusing adjustment at the lower end; thus the
microscope focuses by twisting the main tube. The screw
threads of the focusing adjustment are rather fine
allowing slow movement of the tube for accurate
focusing. The stage, diaphragm disc, mirror case,
ocular, and objective are of brown-colored hard rubber
(Vulcanite).
It is signed on the tube
in fancy script, "Bausch & Lomb Optical Co.,
Rochester N, Y," This is one of the earliest models
made by this firm, possibly the firm's first production
model; the construction is unique, and it was
discontinued sometime before 1878. The screw tube
focusing was later replaced by a sliding tube or rack
and pinion (see the later, but similar,
Educational Model also in this collection). The
microscope was found without its storage case and no
serial number; however, the underside of the base has
eleven punched indentations of
uncertain significance. A similar microscope is in the
Billings Microscope Collection
(see: fig 134 on page 72 of the catalog); it differs
from the present example in having a brass limb as
opposed to the cast iron limb used on the microscope
shown here. An additional example with the iron limb is
in a private collection; it bears the serial number 32,
which is stamped onto the inside bottom of the wood
storage case.