We use Optical Character Recognition (OCR) during our scanning and processing workflow to make the content of each page searchable. You can view the automatically generated text below as well as copy and paste individual pieces of text to quote in your own work.
Text recognition is never 100% accurate. Many parts of the scanned page may not be reflected in the OCR text output, including: images, page layout, certain fonts or handwriting.
286 MICRO-PROJECTION WITH SUNLIGHT [Cn. IX
better source of light for the microscope than the lime light, and now electric lighting is so common that one can use almost any room in a house or laboratory at night for a projection room.
Of course one should not expect too much, but for small audiences — 50 to 100 — and with a moderate sized screen — 2-3 meters — (6-10 ft.) astonishingly satisfactory micro-projection can be done.
§ 418. Hand-feed and automatic lamps for small currents. —
Most of the small current lamps are of the hand-feed type whatever the form of the electric current (a. c. or d. c.) but some automatic ones have been constructed (fig. 44, 205). Large arc lamps may, by special arrangement, be so adjusted that they give good results automatically from 5 to 25 amperes (e. g. the automatic lamp of A. T. Thompson and of the Bausch and Lomb Optical Co., fig. 186, 187).
As for the usual lantern arc lamps, only those for the direct current have hitherto been constructed of the automatic form.
For a full discussion of the wiring and setting up of the apparatus see Ch. Ill and XIII, § 128 and fig. 3, 40, 45.
Do not forget that a rheostat or ballast of some kind must be used on every outfit where an arc lamp is employed (§ 129, 748).
Remember the precautions for turning on and off the current when using the house circuit (§ 133). For a further use of these small currents in drawing, see Ch. X, § 486.
MICRO-PROJECTION WITH SUNLIGHT
§ 419. This was the first light used for micro-projection and remains the best. If it were only available at all times it would be universally employed.
§ 420. Arrangement of the parts of the apparatus. — For the
heliostat to keep the sunlight in a constant position one should consult Chapter VI.
After getting parallel light from the sun in a constant position, then one should use the proper condenser (fig. 74). The remainder of the apparatus is precisely as for the projection so far discussed and all the requirements of centering and arranging at the proper