PROCEEDINGS OF THE SOCIETY. 201 



5. Mechanical Stage. — Not required, but provision made for its later 

 addition. 



6. Sub-Stage Condenser. — Abbe type, accurately centred and fitted 

 with iris diaphragm. 



7. iVose-/?<eC(?.— Dust-proof. Position of objectives marked on nose- 

 piece. 



8. Objectives. — Two, of focal length 16 mm. and 4 mm. (or their 

 equivalents), the latter with good working distance, both engraved with 

 focal length, N.A., tube length and the magnification at the distance 

 for which the objective is corrected, expressed by X ... . 



9. Oculars. — Two, of focal length 40 and 25 mm. Each ocular 

 should be engraved with the initial magnification, the focal length in 

 mm., and with a magnification number arrived at by dividing 250 by 

 that focal length, and expressed by X ... . 



The microscope should be capable of carrying the additions required 

 for more advanced work. 



Type II. — A good instrument for advanced pathological work, price 

 £15 to £20. 



1. Stand. — -Modified Continental jug-handle type, with spiral rack 

 and pinion coarse adjustment. 



2. Tube. — Short, with graduated draw tube ; the scale to allow for 

 length added to the tube by the changing device (viz. nose-piece). The 

 available tube length should be from 140 mm. to 180 mm. 



3. Fine Adjustment. — Lever type. Lateral milled heads of small 

 diameter but long milled surface. 



4. Stage. — Large. Square, with sufficient room to accommodate a 

 large Petri dish. Clips of simple description, having points of contact 

 level with equator of stage. 



5. Mechanical Stage. — {a) Detachable type ; rack and pinion covered 

 through entire length and actuated by milled heads of small diameter^ 

 but with long milled surface. Must work smoothly and permit of 

 examination of at least 2 in. of a 3-in. slide, (b) Built-in type. 



G. Sub-Stage Condenser. — Abbe type. Rack and pinion, centreings 

 iris diaphragm. 



7. Triple Nose-piece. — Dust-proof ; position of the three objectives 

 to be marked on nose-piece. 



8. Objectives. — Three of 16 mm., 4 mm., and 3 or 2 mm. oil immer- 

 sion. Colour of mount of immersion lens to differ from others, and 

 preferably to be black. Each objective should be engraved with the 

 tube length, the N.A., and the magnification at the distance for which 

 the objective is corrected, expressed by X ... . 



9. Ocidars.— ^T wo, of focal length of 40 and 25 mm. Each ocular 

 should be engraved with the initial magnification, the focal length in 

 mm., and with a magnification number arrived at by dividing 250 by 

 that focal length and expressed by X ... . 



