STUDENTS’ MICROSCOPES. 323 
SYNOPSIS OF STUDENTS’ MICROSCOPES. 
MODEL, 
Must have joint to incline at various angles from horizontal to perpen- 
dicular. : 
Ourved Bar. — “ Jackson” (but not prolonged beneath stage); stead- 
iest form for equal weights. 
Transverse Bar. — Most convenient in some respects. 
: WEIGHT. 
Four to ten pounds. — A question of convenience vs 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. 
IAMETER OF TUBE. (1 to 1 3-8 in.) 
Small. gage best and is steadiest on small instruments. 
Large. — Gives wider field with low power oculars. 
MATERIAL. 
All Brass. — Looks best. oa 
Tron Base. — Saves expense, Wears well unless broken by falling. 
COARSE ADJUSTMENT. 
Rack and Pinion. — Easiest; ; preferable but costly. 
Friction Pinion. — Said to be very delicate. 
Chain Movement. — Fine motion. Easily repaired if necessary. 
Sliding Tube, by hand. — Saves expense. Most delicate, but awkward. 
Wants expert hands, and often two of them. 
ADJUSTMENT. Essential. 
Screw and lever movin ng nose-piece. —Best. Costly. d 
Screw and lever moving compound body. TER for ON powers. 
Screw moving compound body. — Less delica 
Screw against shoulder, moving nose-piece. — Moi delicate. 
ew on nose-piece. — Little used. 
Screw mov moving stage. — Cheapest in use in this country. Bad in theory 
i pap puya ; but quite satisfactory in use, as made at present. 
moving pinion of rack. — Not in this country. Good od for low powers. 
May be added to instruments having no other fine adjustment. 
Mechanioat. Nöt nišid. STAGE. 
Lever. — Plausible, but not successful. 
Magnetic. — Plausible, but a pean (Insecure.) 
Sag nd movement. (In two rectangular directions.) — Best substitute for 
ical, for high powers, and with Maltwood Finder. 
Glass, concentric. — Best for Binocular. 
