Accession No
0163
Brief Description
achromatic compound microscope; made by Andrew Pritchard; 1838 - 1854
Origin
162 Fleet Street; London
Maker
Pritchard. Andrew
Class
microscopes
Earliest Date
1838
Latest Date
1854
Inscription Date
Material
metal (brass); wood; glass
Dimensions
height 423mm; depth 245mm; breadth 211mm; box height 349mm; depth 234mm; breadth 264mm;
Special Collection
Robert Whipple collection
Provenance
Purchased by Robert Stewart Whipple from T. H. Court on 21/05/1924.
Inscription
‘Andrew Pritchard’
‘162 Fleet Street’
‘London’
‘No110’
Description Notes
Pritchard model, brass. Tripod stand, brass column. Compass joint to limb. Mechanical stage. Tail piece with swinging concave mirror. Triangular arched column within limb. Knurled screw gives coarse focus. bar limb with screw clamp. Screw fit body, fine focus on body, rotating diaphragm, stage forceps, stage clips. There are six objective all contained in a case. They are ‘1in’, ‘2/3in’, ‘1/3in’, ‘1/12’, and signed ‘A. Pritchard/162 Fleet Street./London’. 2 eyepieces one with a lens cover marked ‘B’. A lid for ‘Lieberkuhn’ Live tube holder, 2 cases for ‘Polarizing Apparatus’ ‘Analiser’ and ‘Polarizer’. a key. Fitted wooden case with three drawers and carrying handles.
5 objectives: height 50, 42, 40, 39, 42mm; max diameter 27, 27, 27, 28, 28 mm respectively, eyepiece height 55mm max diameter 33 mm; polarising apparatus height 44mm; max diameter 47 mm; forceps length 105 mm, breadth 27 mm.
unidentified samples in glass slides found in box. Loose leaves and paper canister with organic material contained also found in box. Also a locked drawer with unknown contents. None of these items appeared previously in the description notes (05/11/2013)
References
Events
Description
When light travels through an ordinary lens each colour is bent through a different angle. In a microscope this causes what is known as chromatic aberration, whereby a spectrum of colours will appear around the image being viewed. Chromatic aberration was a big draw back when using early versions of the compound microscope.
Chromatic aberration was overcome due to the important work by Lister in 1830 who developed the achromatic lens for microscopes. The new type of lens prevented colour separation by combining two lenses made of different types of glass. The first lens that light passed through would split the colours and the second lens acted to bring the colours back together again. This produced a much sharper and clearer image than was previously achieved.
In the Victorian period the achromatic microscope became a vital tool in medical and scientific research. Improvements to the optical performance of the microscope saw developments in the design and construction of the microscope. The microscope became sturdier and could focus to a finer level.
Scientific instrument makers in the Victorian period who improved the rigidity of the optical tube and the focusing ability of the achromatic microscope include Andrew Ross, James Smith and Hugh Powell.
Andrew Pritchard was working, mainly on microscope manufacture, from 1827 until 1854, but by 1845 his instruments had been outclassed by those of Ross, Powell and Smith.
FM:42593
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