. The microscope; a simple handbook. Microscopes. ILLUMINATING APPARATUS 47 for colour screens or ground glass. It is supported on a rod (L) wMch moves backwards and forwards parallel with the optic axis for obtaining either parallel or convergent light, and can be clamped in any position. If the condenser is not required it can be swung to one side; or if it is required to use colour screens alone, the lens of the con- denser can be removed from its mount. The illustrations show the lamp (Fig. 38) for use with the mirror of the microscope for transparent or dark-ground illumination by means o
. The microscope; a simple handbook. Microscopes. ILLUMINATING APPARATUS 47 for colour screens or ground glass. It is supported on a rod (L) wMch moves backwards and forwards parallel with the optic axis for obtaining either parallel or convergent light, and can be clamped in any position. If the condenser is not required it can be swung to one side; or if it is required to use colour screens alone, the lens of the con- denser can be removed from its mount. The illustrations show the lamp (Fig. 38) for use with the mirror of the microscope for transparent or dark-ground illumination by means of a dark-ground condenser, or for metallurgical or photomicrographic work. Fig. 39 shows it tilted for use without a mirror, or Fig. 40 shows it arranged for the illumination of opaque objects from above. The lamp is pro- vided with a ground glass and a signal- green glass ; it is com- pleted by the addi- tion of the Wratten & Wainwright's colour filters and the neutral glass moderator. It is provided with 12 feet of cable and an at- tachment for fitting it to a lamp fitting of an ordinary house supply. For use with the " Pointolite " lamp, which is an in- candescent disc about the size of a small peppercorn, a direct current of any voltage from 100 to 250 volts is equally satisfactory, a variable resistance being supplied to adapt it to any current between these limits. The candle- power is 100, but as it is all concentrated in the one point it is at least twenty times as powerful as the filament lamp focussed with the condenser. If a 100-candle-power 1/2-watt lamp or 40- or 60-candle- power metal filament lamp is used, it is suitable for either direct or alternating currents, and for a voltage from 100 to 200 volts, although a lamp suitable for the voltage must be selected. No special wiring is required, any ordinary house current being Fig. 40.—No. 3332, "Pointolite" Please note that these images are extracted from scanned page i
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