Page:Popular Science Monthly Volume 89.djvu/461

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Popular Science Monthly


��How to Rid Your Yard of Cats

Ct)XSIUHR.\15LE aimisement may be dorivfd from a tlcvice which effectually rids any backyard of stray cats.

There arc many who may find it to be somewhat of a comfort as well as an amusement, if the number of these feline nocturnal musicians in the neighborhood is larger than is appreciated.

Nail two copper wires along the top of the fence, i in. apart, care being taken that they do not touch. Fasten them to insulated wires leading to the secondary of a spark-coil in the house. Connect the coil in series with si.x or more batter- ies and a switch.

When the cats appear on the fence, close the switch. The effect of the shock varies with the nature of the cat,

���Spark CoiJ-

��Arrangement of Wires Along Fence Show- ing One Battery and Switch

but in every case the cat will move on. A similar arrangement can be attached to a garbage can, which must stand on a dry board. The wire leading to the can is insulated, and the other should be grounded. — Alexander Bollerer.

To Stop the Milk Thief

NO one need be deprived of cream for his coffee by some hungry dividual who steals his milk bottle from the porch. The device shown here will effectively prevent any such occurrence.

The apparatus is connected with a switch, bell and battery, and when any one attempts to lift the milk bottle, the bell is rung.

The bottle stands upon a metal disk to the center of which is joined a hea\y wire, which runs through the flooring where it terminates in a loop. Through this loop runs a flat spring, which is helfl away from a large screw by the weight of the bottle. When the bottle is lifted the spring raises the disk and

��touches the large screw, forming a contact and giving the alarm.

By studying the diagram it will be noticed that one wire is soldered to a support on which is hinged a small rod insulated on one end and contacting with a small L-shaped bar, through which the current runs to the large screw. This part of the apparatus is an automatic switch.

When it is desired to set the switch, the disk on which the bottle should stand is pulled up, and the lower end of the wire loop bears against the small rod which breaks the circuit. The switch is turned on in the house. When the bottle is set upon the disk the contact is broken at the large screw, and the small rod is forced into its original position by making a contact with the L-shaped bar.

If the bottle is removed before the house switch is opened, the spring rises with the disk and makes a contact, but owing to the play in the loop, does not break the circuit through the rod. The circuit can only be broken by pulling the disk up farther than the spring can force it.

With this arrangement, it is absolutely impossible for any one to steal the bottle without your knowledge. Of course, the milkman must be instructed to be sure to set the bottle upon the disk each day. — Ed. Gettins.

���/nsulated Tif/ ^OocH Spring

��Mechanism of the Automatic Switch for Catching the Milk Thief

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