The paper is exposed, developed and fixed by the
directions that are enclosed in the package of bromide papers.
[Illustration: Making Large Pictures with a Small Camera]
** Positioning A Hanging Lamp [111]
Don't pull a lamp hung by flexible cord to one side with a wire
and then fasten to a gas pipe. I have seen a wire become red hot
in this manner. If the lamp hung by a cord must be pulled over,
use a string.
A Curious Compressed Air Phenomenon [111]
Push a pin through an ordinary business card and place the card
against one end of a spool with the pin inside the bore, as shown
in the sketch. Then blow through the spool, and it will be found
that the card will not be blown away, but will remain suspended
without any visible support. This phenomenon is explained by the
fact that the air radiates from the center at a velocity which is
nearly constant, thereby producing a partial vacuum between the
spool and the card. Can the reader devise a practical application
of this contrivance?
[Illustration: Experiment with Spool and Card]
** Simple Switch for Reversing a Current [111]
Take two strips of copper or brass and fasten them together by
means of gutta-percha (Fig.
Pages:
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276