bottom of the tubing. The water loosened the sand, and it was carried up and out of the hole with the overflow.”
After we had seen our fill of the shaft-sinking, Mr. Williams took us over to the next building, and showed us how plunger-elevators are operated.
“These elevator-shafts are not nearly as long as the ones we are building next door. They are only two hundred feet high.”
We watched one of the elevators go up, pushed by the light plunger of hollow steel only six inches in diameter. Beads of water trickled down the black, oily surface. As the car went up higher and higher, the slender plunger began to sway as if it were a flexible rope. The car was carrying a heavy load of passengers, and I supposed that that was the reason for the unsteadiness of the plunger.
“It does not seem to be standing the weight very well,” I said. “It looks almost as though it would buckle.”
“Weight!” he quoted. “Why, that plunger is not doing much more than to carry the passengers. The counterweight balances about eighty per cent, of the weight of the car and the plunger. I don’t know exactly what these plungers weigh, but in our elevators next door they will weigh close to five and one half tons. If you loaded one of them on a truck, it would take four horses to draw it. But if the cables to the counter-weight should break, the car would buckle and crumple up that tube as if it were made of rubber.”
“That would break the force of the fall, at any rate,” remarked Will.
“Yes, if the tube did n't snap in two, and a jagged piece of it pierce the floor of the car, and injure one or two of the passengers.”
“But suppose the plunger broke off and the counterweight cables did n’t?” I suggested.
“Why, the car would be relieved of the weight of the plunger, and it would shoot up to the top of the shaft like a rocket. But an accident like that is next to impossible. Yet I did once hear of a case when a car was undergoing repairs. In overhauling the car, the plunger connection had been carelessly loosened without fastening the car down, when suddenly, without any warning, the strain of the counterweight wrenched the car free from the plunger, and up it shot, smashing itself free at the top of the shaft, and then falling down to the bottom again. But such a combination of carelessness would probably never happen again, and the plunger-elevator can be regarded as a pretty safe kind.”
Mr, Williams then showed us through the power plant, and explained how the pumps kept the pressure tank up to the proper pressure, and that each tank had some air trapped in it which acted as a sort of spring, so that, when the elevator man turned the valve lever and the water rushed into the plunger cylinder, it was forced out at a constant pressure by the air; and when he turned the valve the other way, the water poured out of the cylinder into a reservoir, being squeezed out by the weight of the car and the unbalanced weight of the plunger. When the pressure in the tank fell too low, a pump would start up automatically and pump water out of the reservoir into the pressure tank until the desired pressure was restored.
Fortunately no accident befell us on this occasion, and we had a very tame story to report to Mr. Hotchkiss. But although there was nothing very thrilling and deliciously exciting about elevators and “jump” drilling, we felt that we had learned something worth while; also it made an interesting page in the diary that Uncle Edward had asked us to keep. I had taken over the task of writing the diary, because it seemed to me that, in this way, I might repay in a small measure my obligations for the fine vacation I was having at Uncle Edward's expense.
Chapter IX
QUENCHING A CITY'S THIRST
We ran to the bridge across the “transverse” to see what was going on. As we watched, a cage rose quickly to the top of the head-frame, a car tilted forward, its end gate swung open, and out poured a load of broken rock into a large hopper beneath. Then the cage started down again, dragging the car back with it into the shaft. It was a rather deep shaft, too, judging by the length of time that the cable was unreeling. Down in the “transverse” below the hopper was a cart taking on a load af rock.
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