Andrew Pritchard, 162 Fleet Street, London, No. 124

The Standard Achromatic Microscope, c. 1843

Andrew Pritchard Standard Acromatic Microscope Andrew Pritchard Standard Acromatic Microscope
Andrew Pritchard Standard Acromatic Microscope Andrew Pritchard Standard Acromatic Microscope
Andrew Pritchard Standard Acromatic Microscope Andrew Pritchard Standard Acromatic Microscope

Andrew Pritchard Standard Acromatic Microscope spring stage

Andrew Pritchard Standard Acromatic Microscope

The accessories remaining with this microscope include two eyepieces, a non-original objective, a sub-stage aperture disk, a sub-stage polarizer, an analyzing prism mounted in an objective, a stage mounting condenser, a Bonanni type spring stage, and a key to tighten the inclination joint. As shown in the photos, inclined the microscope measures about 18-inches in height. Height can be extended considerably utilizing the telescoping pillar which is a common feature found on many Pritchard microscopes (last two upright images). The microscope is signed with the name and address on the tube and on the tripod base. It is also marked with the serial number, No. 124.

The following was extracted from the book Microscopic Objects by Andrew Pritchard, 1847:

Description of a Standard Achromatic Microscope — The aim in the construction of this instrument has been to obtain the most perfect and effective mounting for the glasses of a microscope; portability and expense being of secondary consideration. The principles on which it is built, and the mode of using it, are fully described in the ‘Microscopic Illustrations’ The perusal of that work, with the help of the following engravings, in which the latest improvements are represented, will enable any person to become familiar with its capabilities and to conduct satisfactorily the investigation of any department of science requiring the aid of the Microscope. The optical part is so fully discussed by Dr. Goring in his works on the Microscope, that it will be unnecessary to enlarge upon it here, further than by stating that the object-glasses consist of combinations of pairs of cemented lenses, whereby the largest amount of penetration and definition are associated with the greatest space between the object and the front lens compatible with the perfect correction of achromatism and spherical aberration.

Pritchard Standard Acromatic Microscope-1847

Description of the Engravinga is the eye-piece, b the body, c the arm into which the body screws. This arm and screw are sufficiently stout to carry the body without vibration, and therefore braces are unnecessary. d is the object-glass ; e the triangular gun-metal bar, having a rack cut in its posterior truncated edge. This rack has a pinion working into it, the large triple-milled head of which is represented at f. The stage g has four holes at the comers, either of which will receive forceps, condenser, or other apparatus. The centre of the stage has an aperture one inch and a half in diameter, into which fits, by a bayonet-joint, the spring safety slider-holder k. This slider-holder has two moveable plates, so that in experiments with polarized light a plate of selenite inserted between them is not disturbed, while the slider with its object, which rests upon the upper moveable plate, is moved about, h is the stem of the microscope, which can be brought into any position, either vertical, horizontal, or inclined at any angle. It will also revolve about its axis within the socket r. This latter motion is of great importance, and no microscope defective in this particular can do half the work it ought, j the mirror ; n the pillar, which consists of two tubes, one sliding within the other, by means of which and the tightening ring m the microscope can be raised or lowered at pleasure. i the solid tripod foot, which has its two posterior prongs squared so as to fit readily into a cabinet nine inches wide by seven inches deep. The anterior prong of the foot has a hole to receive an arm for carrying a candle-holder, large condenser and shade, when required.

Pritchard microscope in the horizontal position

The microscope can also be placed in the horizontal position and rotated 90° in the horizontal plane as shown in the above illustration. This is convenient when observing live specimens in water (with the vial holder stage attachment p) or when using a camera lucida.

Andrew Pritchard (1804-1882) biography

An essay about Andrew Pritchard, his microscopes, and specimen slides is online.

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