Page:St. Nicholas (serial) (IA stnicholasserial402dodg).pdf/605

1913.] now; we are pretty close to our dumping-grounds.”

Presently, there was a rattle of machinery. The two worm-shafts began to turn, making the large hand-wheels rotate slowly, and feeding the screw-shafts downward.

“They are just ‘cracking’ the load,” explained Mr. Porter, “to see that everything is all right before dumping.”

“Cracking!” we exclaimed.

“Yes, they have just slightly opened the gates in the bottom of the bins to see that they are not stuck, so that, when we dump the load, all the gates will operate together.”

“But you don’t mean to tell us that you dump that stuff out through the bottom of the boat?”

“Certainly I do.”

“But why does n't the boat sink when you let the water in?”

“That ’s a foolish question.” said Mr. Porter, “Stop and think about it a moment. Which is heavier, sand or water? Why should this boat sink if we swap a load of sand for a load of water? As the water comes in, the sand falls out, and the boat, relieved of the weight of the sand, actually rises ten feet higher out of the water,”

When they were “cracking” the bins, the sand sank a trifle, but presently the worm-shafts began to turn again, and, out of troughs at each side, there was a rush of water. The sand sank rapidly, and melted away under the stream.

“They ’re running the pumps now to wash dawn the sand,” Mr. Porter explained. “It gets pretty well packed, and does not fall through the gates fast enough unless we help it along with some water.”

As the sand fell away, we saw how enormous the bins were. “Each bin holds fourteen hundred cubic yards,” said Mr. Porter, “and in the two bins there is something like forty-five hundred tons! But, pshaw, I don't believe that conveys any idea to you. If you had to transport this sand overland, yon would have to load it on a train a mile long, made up of one hundred and seventy-five cars, to carry off what this one vessel transports so easily. And what 's more, it took us only two hours and fifty minutes to take on the load. We have been working here steadily for ten years, so you can just imagine we have sucked up quite a bit of mud and sand out of this old hay. The total excavation amounts to nearly seventy million cubic yards!”

Mr. Porter paused, evidently expecting us t0