LARGE MICROSCOPES 41 



although exceptionally massive, it does not give perfect 

 stability when the tube is horizontal unless clamped. 



Zeiss, No. I (Fig. 15), is a typical Continental stand 

 of the very best construction. The makers supply a 

 special rotating and centring mechanical stage, with 

 very slow movements governed by coaxial milled heads 

 for photomicrography, but the ordinary stage is pre- 

 ferable for most purposes ; in this the vertical movement 

 is built into the stage, the bar carrying the lateral move- 

 ment is removable. The substage is simpler than that 

 illustrated in Fig. 14 ; it is focussed by rack and pinion, 

 but does not carry centring screws. The Berger fine 

 adjustment is very good, and fitted with lateral milled 

 heads ; the body tube is of wide diameter. A simpler 

 stand of similar construction, but without mechanical 

 stage and wide tube, is shown at Fig. 27. 



Leitz Stand "A " (Fig. 16) is another fine Continental 

 design with considerable difference in detail from Zeiss' 

 No. 1. The body-tube and fine-adjustment position 

 are similar to the latter, as also is the compact sub- 

 stage arrangement. But the handle-arm is of different 

 form, and gives this stand, and some of the cheaper 

 ones of this make, a distinctive appearance. The me- 

 chanical stage is an adaptable one, but of very sound 

 construction ; its omission would reduce the cost of 

 the stand by 4. The stage is circular, revolving, and 

 centring. The fine adjustment is of a special safety 

 pattern depending on the rotation of a cam. 



Baker's " E.M.S" (Fig. 17). This stand is of the 

 English pattern, but simpler than the " Van Heurck." 

 The substage is of the usual rack-and-pinion and centring 

 type, but cannot be swung out of the optical axis ; 

 it can be fitted with fine adjustment or not, as desired. 

 In the form of the body, position of fine-adjustment 

 heads, and mechanical stage it resembles the Zeiss No. 1, 

 though differing in constructional details. The fine 



