t is not necessary to have a large camera to do this,
as the process is exceedingly simple to make large pictures from
small negatives with the same hand camera.

A room from which all light may be excluded and a window through
which the light can enter without obstruction from trees or nearby
buildings, with a shelf to hold the camera and a table with an
upright drawing-board attached, complete the arrangement. The back
is taken out of the camera and fitted close against the back of
the shelf, which must be provided with a hole the same size and
shape as the opening in the back of the camera. The negative used
to make the enlarged print is placed in the shelf at A, Fig. 1.
The rays of the clear, unobstructed light strike the mirror, B,
and reflect through the negative, A, through the lens of the
camera and on the board, as shown in Fig. 2. The window must be
darkened all around the shelf.

After placing the negative and focusing the lens for a clear image
on the board, the shutter is set and a bromide paper is placed on
the board. 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. 1); also provide them with a handle.
Saw out a rectangular block about one and one-half times as long
as the brass strips and fasten to it at each end two forked pieces
of copper or brass, as in Fig. 2. F