102 



K'MMAHY OF (TL'L'KNT liKSFAIiCHES HELAT1NG TO 



always set in the vertical position, and fig. 21, which omits the bellows, 

 shows its adaptation to the more delicate requirements. F is an iron 

 horseshoe-shaped foot carrying a vertical board B which acts as the 

 pillar of a Microscope. On the lower half of this board two projecting 

 bearers T support a mirror S, 15 by 17 cm., rotatory about a hori- 

 zontal axis, and removable, if required, by single hand-use. To the 

 upper half of this vertical board is attached an arrangement V which 

 allows the object-table to rise or fall about 6 cm. by the action of a 

 micrometer screw M. By means of a lengthening rod, applied at a ball- 

 joint K over the rack of the micrometer screw, the micrometer screw 

 itself can be actuated at a greater distance away — a necessity often felt 



Fig. 21. 



with increased bellows extension. Thus the fine-adjustment is attained 

 by movement of the object-stage, which has the advantage that for 

 a selected objective and a selected bellows length the magnification is a 

 known quantity. The arrangement of the upper part of the apparatus 

 closely resembles that of a Microscope. A sleeve H fitted to the hori- 

 zontal slab A carries a tube C 15 57 mm. wide and 105 mm. long, within 

 which, on its under side, a second tube D, cloth covered, is inserted, its 

 lower end being threaded for the reception of an ordinary micro- 

 objective, or projection-objective, E. For diminutions or for photo- 

 graphy in natural size, other tubes C 2 of similar width and thread can 

 be inserted. At the upper end of the tube C, a short tube G can be 

 used for carrying the narrower tube g of an ocular. This arrangement, 

 of course, reproduces a Microscope, but is useful for determining the 



