The place of the test, as I have said, was in a deserted spot. On one side of a great valley the gun was being set up. Its muzzle pointed up the valley, toward the side of a mountain, into which the gigantic projectile could plow its way without doing any damage. Tom was going to fire two kinds of cannon balls—a solid one, and one containing an explosive.
The gun was so mounted that the muzzle could be elevated or depressed, or swung from side to side. In this way the range could be varied. Tom estimated that the greatest possible range would be thirty miles. It could not be more than that, he decided, and he hoped it would not be much less. This extreme range could be attained by elevating the gun to exactly the proper pitch. Of course, any shorter range could, within certain limits, also be reached.
The gun was pointed slantingly up the valley, and there was ample room to attain the thirty-mile range without doing any damage.
At the head of the valley, some miles from where the giant cannon was mounted, was an immense dam, built recently by a water company for impounding a stream and furnishing a supply of drinking water for a distant city. At the other end of the valley was the thriving village of Preston. A railroad ran there, and it was to
