1900] MICROSCOPICAL JOURNAL. 291 



The stage is square, the upper surface being faced with 

 an ebonite surface. In the instruments Nos. 1125 and 1129 

 it measures 3iin. by 3iin. In the large model instru- 

 ments Nos. 1152 and 1153 it is specially large for the 

 examination of Petrie dishes or culture plates, and meas- 

 ures 4in. by 4in, A removable mechanical stage can be 

 attached at will to any of these instruments without re- 

 turning the microscope to us. 



The coarse adjustment is by spiral rack-and-pinion, so 

 accurately fitted that even comparatively high powers can 

 be focussed thereby. The fine adjustment, which is very 

 delicate, consists of a triangular prism upon which slides 

 smoothly a solid metal sleeve which fits this prism so 

 perfectly that there is no lateral motion. 



The adjustment is obtained by a fine micrometer screw 

 actuating a supplementary pointed rod which impinges 

 upon a hardened steel plate. 



The limb of the microscope is so designed that there is 

 a plenty of room for the fingers when turning the milled 

 heads. In the larger model instruments, No. 1152, 1153 

 the milled head, which is of a larger size, is graduated to 

 1-2,000 in, for measuring the thickness of cover-glass, etc. 

 and a folding indicator is attached to the limb of the in- 

 strument. 



The body tube of the microscope is 140mm. long with a 

 graduated draw-tube which extends the length of 200mm. 



A double mirror on a swinging arm is provided, and in 

 microscopes Nos. 1125, 1129, an iris diaphragm accom- 

 panies each instrument. The latter is made with a fitino- 

 at the top into which may be fitted a small Abbe form con- 

 denser. Tiie instrument, No. 1129, is provided with a 

 spiral focussing and swing-out adjustment. The larger 

 model microscope, No. 1153, has the same substage as No. 

 1129, while the No. 1,152 has a complete rack-and-pinion 

 focussing substage with centering adjustments. 



The Abbe CQudenser is supplied in two sizes — in both 



