BEXJ. PIKE'S, JR., DESCRIPTIVE CATALOGUE. 



Rons Compound Achromatic Microscope, No. 2. This 

 instrument (Fig-. 789) consists cf A, compound body; B, 

 mirror; C, stage for holding- object to be examined; D, 

 pinion with milled head to adjust the object-glasses to 

 their focus ; E, round brass column supporting- stage and 

 mirror; F, pillar, with cradle-joint; G, tripod stand; H, 

 condenser; I, steel forceps; K, extra eye-piece; L, 

 object-glass with low power; M, dissecting-knife ; N, 

 dissecting-point ; O, brass forceps ; P, slider, containing 

 test-object; Q, slips of glass; 11, fluid box. This instru- 

 ment, though one of moderate cost, is both in respect to 

 its achromatic lenses and its mounting, of the finest work- 

 manship ; its construction is convenient and elegant. By 

 means of the cradle-joint the instrument may be used in 

 a horizontal, inclined, or vertical position, and for general 

 purposes has no superior at its price. 



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, Avhich 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 dia- 

 phragm, 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 con- 

 denser. 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 re- 

 flects 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 move- 

 ment, the rays reflected from the concave mirror may be 



