ZOOLOGY AND BOTANY, MICKOSCOPY, ETC. 97 



piece of the Microscope is 4*1 in. from the stage. The fine focussing 

 adjustment is upon a new patented method invented by Mr. Ashe. A 

 strong lover moves the cradle, which carries the body of the Micro- 

 scope by means of a block which is a projecting portion of the cradle. 

 The cradle slides in a fitting in the limb with a spring acting upon the 

 upper side of the projection, which drives it on to the lever. The lever 

 is moved by a steel screw with milled head ; this screw works through 

 an outer screw which is provided with a large graduated milled head, 

 read by a folding indicator. 



One screw has a comparatively coarse thread, and when revolved 

 raises the body a distance of ^V^ 1 f an iuch in a complete revolution. 

 The other screw has a fine thread, and when revolved carries the former 

 screw with it, moving the body only ^^th of an inch in a complete re- 

 volution. At any moment either milled head may be used, giving a 

 moderately fine adjustment for such powers as {-in. or -J-, or a very 

 fine movement for T V or higher poAvers. The convenience of such an 

 arrangement can scarcely be overstated. 



A slow motion fine enough for focussiug the highest powers is most 

 troublesome for moderate-power lenses. 



The Stage. — In the complete model of the instrument the stage is 

 •circular, 5 inches in diameter, with a graduated circle divided in 

 degrees and moved by a rack-and-pinion, which may be thrown out of 

 gear. Centring screws are provided to adjust the centre of rotation. A 

 mechanical rack-and-pinion top stage works upon its surface by two 

 milled heads having a horizontal motion of 2^ in. and a vertical 

 motion of 1^ in. This is so designed that during its whole travel 

 it does not come in contact with the substage condenser. Graduated 

 finder-divisions are provided to both motions for recording and finding 

 again individual points of an object, and for rough measurement pur- 

 poses. When these are used the centring screws should be unscrewed 

 to their full extent in order that the divisions should always indicate 

 the same position. A folding stop for Maltwood's finder and folding 

 springs aro carried by the mechanical stage. Even with the mechanical 

 stage in situ, except in its extreme positions of travel, a complete rota- 

 tion of the stage can be obtained. 



The mechanical stage can be entirely removed, leaving the stage 

 free for large culture plates or dishes. Spring clips are provided for 

 use with the plain stage. 



The simpler models of the instrument are provided with a large 

 square top, 4^ in. by 4^ in., with a removable mechanical stage, having 

 a horizontal travel of 2 in. and a vertical travel of 1-J in. 



The substage is made to the Royal Microscopical Standard size, 

 1*527 in. It has coarse adjustment by spiral rack-and-pinion, and 

 a lever and micrometer-screw fine adjustment. It has two centring 

 screws in directions at right angles. The substage itself has no 

 swinging-out motion, but a mount may be supplied carrying the con- 

 denser, in which the diaphragms and the optical portion swing out. 



The mirror is flat on one side and concave on the other. It is 

 2h in. in diameter, and is swung on a fitting which slides up and down 

 on a dovetailed bar. This bar is held in the optic axis by a spring stop, 

 but may be swung to one side or the other if desired. 



Feb. 19ih, 1902 h 



