CONSTRUCTION OF THE MICROSCOPE. 



45 



mirror, etc., yet, for the class of purposes to which it is suited, it has 

 advantages over perhaps every other form that has been devised. 



44. Quekett's Dissecting Micro- 

 scope. By the Scientific investiga- Eta -82. 

 tor who desires a large flat stage, 

 'Combined with portability, the ar- 

 rangement devised by Mr. John 

 Quekett (Fig. 32) will be found ex- 

 tremely convenient. The Stage, 

 which constitutes the principal part 

 of the apparatus, is a plate of brass 

 (bronzed 1 ) nearly six inches square, 

 screwed to a piece of mahogany of 

 the same size, and about 5-8ths of an 

 inch thick; underneath this is a fold- 

 ing flap four inches broad, attached 

 on each side by hinges; and the two 

 flaps are so shaped, that, when folded 

 together, one lies closely upon the 

 other, as shown at B, Fig. 32, whilst, 

 when opened, as shown at A, they 

 give a firm support to the stage at 

 .a convenient height. 2 At the back 

 of the stage-plate is a round hole, 

 through which a tubular stem works 

 vertically with a rack-and-pinion 

 movement, carrying at its summit 

 the horizontal Arm for the magnify- 



11-10- nnwprc nnH infn +!IP rmrlprdHp Quekett's Dissecting Microscope, set up for use 



ing powers, ana into tne unaersiae at A, and packed together at B. 



of the stage-plate there screws a stem 



which carries the mirror-frame. From this frame the mirror may be re- 

 moved, and its place supplied by a convex lens, which serves as a condenser 

 for opaque objects, its stem being then fitted into a hole in the stage, at 

 one side or in front of its central perforation. The instrument is usually 

 furnished with three magnifiers namely, an inch and a half-inch ordinary 

 lenses, and a quarter-inch Coddington; and these (or the combinations of 

 equivalent foci already mentioned, 25), will be found to be the powers 

 most useful for the purposes to which it is specially adapted. As a black 

 back-ground is often required in dissecting objects which are not transpa- 

 rent, this may be most readily provided by attaching a disk of dead-black 

 paper to the back of the mirror. The lenses, mirror, condenser, vertical 

 stem, and milled-head, all fit into a drawer which shuts into the under- 

 side of the stage ; so that, when packed together, and the flaps kept 

 down by an elastic band, as shown at B, Fig. 32, the instrument is 

 extremely portable, furnishing (so to speak) a case for itself. It may be 

 easily made with an addittional arm carrying a light Compound body, 



1 The Stage-plate is sometimes made of plate-glass or ebonite ; and this is 

 decidedly advantageous where Sea-water or Acids are used. 



2 The Stage is now more generally supported, either (as in Mr. Ladd's model) 

 on four legs of strong brass wire, which screw into its underside, and are packed 

 in its drawer when dismounted ; or (as made by Mr. Swift and Messrs. Parkes of 

 Birmingham) on four brass legs which fold beneath it ; either of these construc- 

 tions remedying the chief disadvantage of the original model, which consists in 

 the exclusion of side light from the mirror. 



