CRAIG MICROSCOPE (Lacquered Brass)
with Seven Accompanying Craig Slides including a Microphotograph
MAKER: Henry Craig
c. 1870
SIGNED ON THE LENS: 'CRAIG'S LENS, PAT'D FEBY.18.1862.'
SIGNED ON THE CASE FOR SLIDES: 'ONE HALF-DOZEN ASSORTED MICROSCOPIC OBJECTS, Fly's Foot, Bee's Sting, Varieties of Human Hair, Wasp's Wing, Butterfly's Wing Dust, Hair of a Mouse,
Henry Craig, 335 Broadway, New York'
SIGNED ON THE MICROPHOTOGRAPH: 'PHOTOGRAPH Lord's Prayer, CONTAINING 268 letters, Henry Craig, 335 Broadway, New York'
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DESCRIPTION:
This is a simple microscope made of thin lacquered brass with a gutta-percha disc holding the lens. The lens housing is about 7/8 inches in diameter. The brass base is about 2 inches in diameter. The microscope stands about 5 inches high. The base is not weighted. There is a slot near the top to admit a slide. The mirror is controlled by a single knurled knob on one side. Inside the optical tube is a blackened disc with a single central hole to limit the size of the lightbeam entering the specimen slide.
In use with a slide, the lens housing(left) is lifted up and the slide put through the slots, then the lens housing is lowered so the bottom rests on the slide. As shown in the diagrams from the patent(right), the lens is actually composed of a sphere of flint glass, fused to a flat piece of crown glass, thus making it somewhat achromatic. The lens bottom is covered with a thin piece of glass at the focal point, such that objects in contact with it would be in focus; it was also intended to have specimens placed directly on this bottom surface, adhering to it by surface tension, as would a drop of pond water. The focus is fixed at the bottom of the lens housing, so it is impossible to do fine work, especially with a specimen mounted under a coverslip. Nevertheless it does allow one to read the words of the microphotograph, and have fairly good views of the specimens in the slide set, which, with thin coverslips, are in reasonable focus. After cleaning, the lens in this example is still not perfect with a thin layer of debris or imperfections that I could not remove.
The enclosed slides are 2 1/4 x 1/2 inch and have thin coverslips under their paper covers. The original box for the slides is about 7/8 inches thick on each side. An inner, originally 5 sided, box slides into the outer box, but its ends are missing. This box of six slides, actually containing seven with the extra microphotograph, even has room for one or two more slides. Not only did Craig offer a six slide set, but also a 12 slide set in a wider box.
The green cylindrical box for the microscope is made of cardboard and, like many examples, has lost one of the two thin ends.
HISTORY OF THE CRAIG MICROSCOPE AND SLIDES
These flimsy microscopes from over 150 years ago, are relatively uncommon in good condition when complete with the lens; the box and slides are even less common. They originally sold without slides for $2 then, about $30 today. This is quite expensive for what the buyer was paying for, and for the same price a much better magnifier or simple microscope could have been purchased. In fact, it is almost easier to use the Craig lens directly on the slide without the rest of the microscope. Furthermore, opaque objects cannot be examined with this lens designed for contact focusing.
For a detailed history of Craig microscopes, including other variations, and the somewhat similar Globe microscopes, please see the article about them on Microscopist.net. WARNING-PLEASE NOTE: If you are intending to buy one of these for your collection, please be careful. Many are sold without the lens, and are therefore of minimal or no value; without the lens, its just a cheap thin piece of metal without any use as a microscope!
