A Most Improved type microscope with advanced features
An early achromatic (and non-achromatic) transitional microscope, c. 1830
The upper portion of the tube having the double eye-lens and field lens can be removed and replaced with an adapter that can accommodate an alternate set of Huygens eyepieces. Two are provided (one lacking its bottom lens) having the outer lacquered portion with a bayonet fitting.
Achromatic objectives and Huygens eyepieces.
The microscope
now known as the "Most Improved" model has its
origin in the "Universal Compound Microscope"
introduced by George Adams Jr. in the late 18th
century and described in his 1787 publication,
Essays on the Microscope.
By the end of the century, the copyright to
Adams' books and designs were purchased by the
firm W. & S. Jones of London. They began,
in 1798, the production of a microscope with a
similar design, which they called the
"Jones
Most Improved Microscope". A folding tripod
base from which rises a pillar terminating in a
compass joint for inclination characterizes
this design. Attached to the other end of the
joint is a bar that holds the tube, stage,
mirror, and sometimes a simple lens to serve as
a condenser. The focusing mechanism consists of
a rack embedded in the bar and pinion attached
to the stage; this arrangement moves the stage
in and out of focus. The mirror can also be
positioned on the bar by sliding it up and
down. The optics in this model usually consist
of a double eye-lens and a field lens located
within the body of the tube; the objectives are
non-achromatic. This design became very popular
and was produced by many other English
opticians during the first part of the 19th
century.
Overall, the
microscope shown on this page, which is
unsigned by its maker, conforms to a "Most
Improved" design, albeit one with some advanced
features among which are a mechanical stage having
the control knobs located on the underside of the stage, a
screw fine adjustment that moves the stage in
addition to the rack and pinion coarse
adjustment, a focusing sub-stage with condenser
(achromatic?), both achromatic and
non-achromatic objectives, an alternate
eyepiece arrangement, a double sided mirror,
a dark well holder built onto the underside
of the stage (three dark wells are supplied),
and a telescoping pillar.
During the period
around 1830-1840 the English microscope was
undergoing a rapid evolution from the
non-achromatic instruments produced in the
previous century to the achromatic microscopes
that became more common within the second
quarter of the 19th century. During this
evolutionary period, some of the microscopes
that were produced are often now referred to as
"transitional"; that is, they represent a
design that is midway between the older and
newer forms. The microscope shown on this page
is clearly one of these.
Certain features
of this microscope are reminiscent to those
produced later by Hugh Powell and Andrew
Pritchard suggesting that possibly this
microscope is an early product of one of these
individuals. It is known that Powell, for
a time, made instruments for the
trade before beginning to sign his own
microscopes around 1840.
On a brass
placque inset into the cover of the case is
worn engraving with the name of a previous
owner, either Tho's Bund or Tho's Brind. In the
London trade directories, there is a listing
for a Thomas Brind (1793-1870) as follows:
"Brind Thos. Coal & coke mercht, 24
Winchester wf, City rd. basin", possibly the
original owner of this instrument?