Science as the use (№ 387687)

In his travels, came to Nasreddin Hodja to a distant village and, passing through the street, he saw a strange sight. To the gate of the lonely old man at the tail was tied a donkey, and every time someone entered the garden and opened the gate, that in turn pulled the poor animal's tail, and he uttered a cry. A curious Hodge, having entered the house, found an old blind man and asked why he settled on that leash? Received a response, the animal gave him grandchildren, he had never seen and did not know about these. Feeling the donkey, blind man found that when pulling the tail, roar. Other applications other than to alert visitors, it the phenomenon could not come up. Then Hodja Nasrudin was asked to change the donkey to a door bell. Both were satisfied, Hodge is no longer necessary to walk, and the blind to remove the manure and feed the door bell.