This section is from the book "The Boy Mechanic Vol. 1", by Popular Mechanics Co.. Also available from Amazon: 700 Things for Boys to Do.
Last summer I was annoyed a great deal by dogs upsetting our garbage can on the lawn, but finally executed a plan that rid the yard of in one afternoon.
I first secured a magneto out of an old telephone, then drove a spike in a damp place under the porch, attached a wire to the spike and ran the wire to one of the poles of the magneto. Then I set the garbage-can on some blocks of wood, being careful not to have it touch the ground at any point. I next ran a wire from the other pole of the magneto to the can, wrapping the wire around the can several times. Then I sat down on the porch to wait.
It was not long before a big greyhound came along, putting his forepaws on the top of the can to upset it. At the same instant I gave the magneto a quick turn, which sent the dog away a very surprised animal. This was repeated several times during the afternoon with other dogs, and with the same result. --Contributed by Gordon T. Lane, Crafton, Pa.
 
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