82 Our Present Medical and Students' Microscopes. 
SYNOPSIS OF STUDENTS’ MICBOSCOPES. 
Model. 
Must have joint to incline at various angles from horizontal to 
perpendicular. 
Curved Bar. — “ Jackson ” (but not prolonged beneath stage) ; 
steadiest form for equal weights. 
Transverse Bar. — Most convenient in some respects. 
Weight. 
Four to ten pounds. — A question of convenience v. firmness. 
Height. (12 to 16 inches.) 
Tall. — Much room below stage. Standard length of tube gives 
usual powers. Looks well, and is most convenient when inclined. 
Short. — Easiest for vertical use. Short tube works lenses at too 
low power. Should be lengthened by draw-tube when inclined. 
Diameter of Tube. (1 to 1 3-8 in.) 
Small. — Looks best and is steadiest on small instruments. 
Large. — Gives wider field with low-power oculars. 
Material. 
All Brass. — Looks best. 
Iron Base . — Saves expense. Wears well unless broken by falling. 
Coarse Adjustment. 
Bach and Pinion.— Easiest ; preferable, but costly. 
Friction Pinion. — Said to be very delicate. 
Chain Movement. — Fine motion. Easily repaired if necessary. 
Sliding Tube, by band. — Saves expense. Most delicate, but awk- 
ward. Wants expert bands, and often two of them. 
Fine Adjustment. Essential. 
Screw and lever moving nose-pitce . — Best. Costly. 
Screw and lever moving ccmpjound body. — Good for moderate powers. 
Screw moving compound body . — Less delicate. 
Screio against shoulder, moving nose-piece. — Less delicate. 
Screw on nose-piece . — Little used. 
Screw moving stage. — Cheapest in use in this country. Bad in 
theory and history ; but quite satisfactory in use, as made at present. 
Bar moving pinion of rack. — Not in this country. Good for low 
powers. May be added to instruments having no other fine adjust- 
ment. 
Stage. 
Mechanical.— Not required. 
Lever . — Plausible, but not successful. 
