[Illustration: Aquarium Finished]
If desired, a centerpiece (A, Fig. 2) can be made of colored
stones held together by cement, and an inverted jar can be
supported in the position shown at B. If the mouth of the jar is
below the surface of the water it will stay filled and allow the
fish to swim up inside as shown. Some washed pebbles or gravel
should be placed on the bottom, and, if desired, a few Chinese
lilies or other plants may be placed on the centerpiece.
** Homemade Pneumatic Lock [65]
Mount an old bicycle hand-pump, A, on the door by means of a metal
plate, B, having a swinging connection at C. Fasten the lever, D,
to the door knob, and make a hinge connection with the pump by
means of a piece of sheet
[Illustration: Pneumatic Door-Opener]
brass, E, soldered to the end of the cylinder. All this apparatus
is on the inside of the door and is connected by a small rubber
tube, F, to a secret mouthpiece placed at some convenient
location. A small piece of spring brass, screwed to the door
frame, will open the door about 1/2 in. when the operator blows in
the mouthpiece, or if the door is within reach of the mouthpiece,
the operator may push the door at the same time that he blows,
thus doing away with the spring, which is only used to keep the
door from relocking.
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