A humorous story in which two men formulate a mathematical "law of scared dogs" to help in frightening away an annoying dog named Fluff.
(quoted from Getting Rid of Fluff)
"I bet if Sir Isaac Newon had had Fluff as long as you have had him he would have had a formula all worked out 
x Ã· y (2 Ã— z  dog)= 2(4ab3x)
or something of that kind, so that anyone with half a knowledge of algebra could figure out the square root of any dog any time of the day or night. I could get up a Law of Dog myself if I had the time, with a dog like Fluff to work on. If one dog travels fourteen hundred and forty miles at the sight of a gun, how far would two dogs travel? All that sort of thing. Stop!" he ejaculated suddenly. "If one dog travels fortyeight hours at the sight of a gun, how far would he travel at the sight of two guns? Murchison," he cried enthusiastically, "I've got it! I've got the fundamental law of periodicity in dogs! Go get your gun," he said to me, "and I will get mine."

After some experimentation with a variety of numbers of guns, they determine that the time a dog will be gone would be inversely proportional to the number of guns. Hence, they later conclude:
(quoted from Getting Rid of Fluff)
Well, the inverse ratio to no guns is infinite time  that is how long Fluff will be gone; that is how long he will run. Why, that dog will never stop running while there is any dog left in him. He can't help it  it is the law of scared dogs.

Thanks to Douglass Keeslar for bringing it to my attention. 