Microscope made by Charles Chevalier

c. 1855

Microscope made by Charles Chevalier

Microscope made by Charles Chevalier, Pike catalog

From: Pike's Descriptive Catalogue of Optical, Mathematical, and Philosophical Instruments, Vol. I, 1856

Description.-To a heavy tripod base is screwed a brass pillar with a cradle-joint at the top; from the moveable part of the joint an arm or cross-piece extends, carrying a circular column, to which is attached the stage, or part on which objects are placed for examination, which is a large flat plate, having a central opening, over which the sliders containing objects for examination are placed; small spring clips moveable up and down in sockets in the stage may be pressed over the slider to secure it from falling, when the instrument is used in an inclined or horizontal position; beneath the stage-plate is the diaphragm, which is a plate of brass perforated with four or more holes of different sizes; this revolves on a pivot so as to bring each hole in succession under the object-glass, and is used in modifying the light in examining minute transparent objects. There is a hole in the stage-plate for receiving the spring forceps, and a socket for the condenser. The mirror consists of a circular brass frame, in which are set two silvered glasses, one concave and the other plane, and two inches in diameter; the former reflects the light in converging, and the latter in parallel rays; for facility of adjustment the frame carrying the glasses is made to turn in every direction, by means of joints, and adapted to a tube fitting the brass column, which may be slid either up or down by pressing two small handles projecting from the sides; by this movement, the rays reflected from the concave mirror may be brought to a focus or not, as required upon any given object on the stage. The compound body is a tube of brass about seven inches long, and one and a quarter inches diameter. It contains the eye-piece at the upper end, and the object-glasses at the other, screwed to an arm having a square bar which is fitted to move by tooth and pinion motion within the round brass column; to its upper end the eye-pieces are adapted, to its lower the object-glasses. As the latter are of different magnifying powers, and also the objects to be examined rarely of the same thickness, it is required that there should be a focal adjustment; this is effected by a tooth and pinion arrangement in connection with the square bar sliding within the round column E, and motion given by turning the milled head, D, by which the whole tube carrying the eye-piece and object-glasses is made to approach or recede from the object. The eye-piece consists of two plano-convex lenses; the smaller one is called the eye-glass, and the larger the field-glass; they are set in brass cells, and mounted in a tube whose length is about equal to half of the sum of their focus. Between the lenses is placed a stop, or diaphragm, for diminishing the spherical abberration. The inside of these tubes, and also of all other parts through which the light passes, is blackened, so that no other rays than those from the mirror should interfere with the illumination. The achromatic object-glasses are three in number, and screw together, being so arranged that one, two, or three may be used according to the magnifying power required. There is also a double convex lens in a cell, useful where a low power is required. The condenser, H, or illuminating lens for opaque objects, is a plano-convex lens of short focus set in a brass frame, and supported by one of its arms in a socket attached to the stage-plate; the arms are jointed, and the lens may be set in any position required to receive the light and condense it on the object to be examined. The steel forceps, I, for holding small objects, are formed at the end of a small wire, and made to slide in a small tube having a pin projecting to fix it in a hole in the stage; the forceps are opened by pressing small studs between the thumb and finger. The dissecting-knife, M, and point, N, are convenient for separating parts of objects, and the brass forceps, O, for taking up small objects. The fluid-box, R, is of brass, with a glass bottom, and used for containing any liquid to be examined. Several test-objects, P, and glass sliders are sent with the microscope. This instrument in the vertical position is from fourteen to fifteen inches high; but the parts are made to separate in an easy manner by screws, and every part neatly and securely packed in a mahogany box with lock and key, the blocks supporting the parts being lined with velvet, and the box, inside and outside, well polished; size of box, ten inches long by eight wide, and three and a half deep. Price $40

Although microscopes of this type are invariably unsigned, they are commonly attributed to the workshop of Charles Chevalier (1804-1859). Nevertheless, this attribution is debatable.

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