138 THE MICROSCOPE 



Uluminator as above in centring substage fitting 

 Stop to fit 1/12-in, oU-immersion object glass to 



reduce aperture for dark-ground illumination 

 Beck patent focussing dark-ground immersion 



illuminator in plain substage fitting 

 Ditto, in centring substage fitting . 

 Bull's-eye condenser, 2J-in. diameter, on heavy 



stand, with full adjustments 

 Bull's-eye condenser, IJ-in. diameter, on 



smaller stand with full adjustments 

 Parabolic reflector ..... 



Parabolic reflector with Sorby reflector . 

 Thin glass reflector ..... 



Thin glass vertical illuminator 



Prism illuminator ...... 



Double-wedge light moderator 



Colour trough ... . . 



Paraffin lamp ...... 



Beck electric lamp, complete with bull's-eye 



condenser, ground glass, signal-green glass, 



and metal filament 60 candle-power lamp . 8 10 



3331 46 Beck electric lamp as No. 3330, but with 100 



caudle-power half-watt lamp . . .900 



3332 46 Beck electric lamp as No. 3330, but with 



" Pointolite " electric lamp, with resistance to 



work off direct current from 100 to 250 volts 14 15 



3333 42 Set of 9 Wratten & Wainwright's colour 



screens, for use with above lamps, com- 

 prising ; light blue, to give daylight colour. 

 No. 78 ; dark blue, dominant wave-length, 

 5,000 ; blue-green, d.om. wave-length, 4,700 ; 

 light green, dom. wave-length, 5,500 ; green, 

 dom. wave-length, 5,350; yellow, dom. wave- 

 length, 6,000 ; orange, dom. wave-length, 

 6,300 ; red, dom. wave-length, 6,500 ; neutral 

 tint, passing 1/10 ..... 



— 42 Single filters, as above . . . each 



— — Stand to hold two filters, as above 



— CSrcular screens to fit substage rings can be 



supplied ..... each 



3337 48 Incandescent gas lamp .... 



— Extra mantles ...... 



3338 48 Incandescent spirit lamp .... 



— Extra mantles . . . . . each 

 3336 45 Electric lamp on stand to take ordinary bulb . 



APPABATUS FOR HOLDING SPECIMENS 



3307 61 Sliding ledge 14 



3305 99 Detachable mechanical stage, as illustrated on 



Microscope No. 3213 (page 99) . . .600 



3306 52 Concentric rotating mechanical stage, as illus" 



trated 12 



3400 52 Glass slips, 3x1, best quality, ground edges, 



approximate thickness 1 mna, per doz, 9 



per gross 8 6 



3401 62 Ditto, second quality, ground edges per doz. 7 



per gross 6 6 



