220 THE HISTORY AND DEVELOPMENT OF THE MICROSCOPE 



instrument in a horizontal position for photo-micrographic work. 

 The microscope is illustrated in fig. 176. 



A modification of this instrument was brought out as these 

 pages are passing through the press, which is entitled to rank as a 

 first-class instrument. It is known as the B.M.S. 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 

 fine adjustment giving a movement of Oil mm. (-^ 5 in.) for each 

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



FIG. 176. Baker's D.P.H. stand No. 1 (1899), 



ten parts, each division being numbered. It also possesses two draw- 

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

 provided with rack and pinion adjustment, so that objectives may 

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

 of the tube length ; these draw-tubes extend to 250 mm., and close to 

 120 mm., either English or Continental objectives can be used ; this 

 microscope has a rotating mechanical stage giving a movement of 

 25 mm. (1 in.) in either direction graduated to J- mm. ( ? L i n .) 

 the milled head of the transverse motion is below the level of the 



