220 THE HISTORY AND DEVELOPMENT OF THE MICROSCOPE 



instrument in a horizontal position for photo-mierographic work. 

 The microscope is illustrated in fig. 176. 



A niodilicat inn <>f this instrument was brought out as these 

 pages arc pissing through the press, which is entitled to rank as a 

 first-class instrument. It is known as the R.M.8. 1'27 gauge 

 microscope, and is illustrated in fig. 177. It has a diagonal rack 

 and pinion coarse movement, and a micrometer screw and lever 

 line adjustment giving a movement of Oil mm. (o4 5 in.) for each 

 revolution of the screw, the milled head of which is divided into 



PIG. ITti. Inker's D.P.H. shuul No. 1 (16'.'.i . 



ten parts, each division lie ing numliered. It also possesses two draw- 

 tubes engraved in mm., every tenth numbered, one of which is 

 provided \\ith rack and pinion adjustment, so thai objectives may 

 be corrected tor the thickness of the cover glass, &c., by the alteration 

 of the tube length ; bhese draw- tubes extend to '-!"><> mm., and close to 

 -" mm., eit her Knglish or ( 'out mental object i\ es can be used ; this 

 microscope has a rotating mechanical stage giving a movement of 

 -"' nim. (I in.) in either direction graduated to \ mm. (.-' in.); 

 'I' 1 ' milled head of the transverse motion is below the level of the 



