Popular Science Monthli/
��771
��lens-board in or out. Remove the slide and adjust the arc-hini[) to remove the bluish spots that will most likely be seen in the field of light. By moving the lamp up or down, to the right or left, or
���A #-
��Fig. 12. Dimensions of the upright which serves to carry the light-shield
back and forth upon the tubes, the field will gradually be made perfectly clear. When the light is uniformly white, the slide may be replaced and a sharp focus obtained by turning the milled, adjusting knob on the lens-barrel. All lenses
��should be ke()t scrupulously clean, since the slightest trace of dust will diminish the brilliancy of the illumination to an astonishing degree.
Lantern-slide plates may be oblainerl from any dealer in photographic ma- terials. The standard size is t,}4 in. by 4 in. in the United States, and all slide- carriers made for use in this country take that size. The lantern slide emul- sion or coating is so sensitive that the slides must be han- dled under ruby or deep orange light only, in order to avoid fogging. With this one ex- ception, they ma>- be handled precise- ly as one would use the popular devel- oping-out papers.
To make the slide, the plate is placed in a print- ing-frame, with its emulsion (dull) surface next to that
���c XiM' avemf mfh /ynp ofdrmj
���Fig. 13. The light shield which is sol- dered to the upright
��of the film or plate from which the print is to be made. The frame is then held at a distance of about 6 ft. from a 25-watt tungsten lamp, and the latter turned on for two seconds. This exposure is correct for the average negative and is cited merely
���Scnsivs muit^ not touch "^R^
���a^T^
��=i^
��.r
��CJeorance i*-!0 a
��^fVnf ^fie^^i brass 'strip z fie^ ^ b'°^ ^^"P ^onwitfi solder 1-
��n
��Rear v/etf
��o/lar
��Sheet iron hood riveted on over large opening
��Oisc of thin gtais
��w^ 4- ^ .^1
i/iec}. fibre
���Jma/t flowerpot fined with fire day
���efleq brass tube sour cuts
��\^r~
^Rea. brass tube
��Clomps irirea on Rear vietv
��■^ 2 Peg fibre I Reg brass
��Fig. 14. Details of the arc-lamp which is adapted for use on comparatively small currents. The carbons are fed by merely twisting and pushing the knobs fitted to their ends
�� �
