OPERATIONS BELOW.
As soon as the sand is dug, it is sent up various pipes, four inches in diameter, which operate in the same way as siphons. It is odd to notice with what force the sand ascends to the top of the caisson, and it is all that six men can do to shovel it in fast enough. Boulders of trap rock were found embedded in the quicksand. These were broken up and hoisted out by an apparatus similar to a dredging machine, working in an immense shaft filled with water.
The shape of the interior of the caisson resembles very much the lips of an enormous bell, and in reality it is worked upon the same principle as an ordinary diving-bell, the water being kept out by the great pressure of air. As soon as the caisson is perfectly settled, and all the sand and debris down to the bed rock is removed, the interior is filled with concrete and masonry, and thus the pier obtains a foundation perfectly solid.
While making a tour through the various chambers, I found a pair of doves, which had been placed there for testing the effect of the compressed air. The birds appeared to have become accustomed to their new habitation, where they had been for several weeks. They looked, however, rather disconsolate and sickly, and I learned, a day or two later, that one had died from the effects of its imprisonment.
A black and tan terrier had also been taken into the caisson, but after it had been down a few hours it became paralyzed in its hind legs, and was taken up; and for more than a fortnight it did not recover from the shock to its system.
SCENES IN THE CAISSON.
The scene in the caisson is a very novel one. The water, seen through the gas jets, sparkles in the pools at the bottom of the river, the men are toiling and perspiring amid the rushing and rumbling noise of the sand siphons, and everything appears in confusion. While our party was making its tour, it was found that our voices had completely changed; each one appeared to stutter, and altogether the voice had a very unnatural sound, as if we spoke in a half screeching key.
An attempt was made to whistle, but whistle we could not. The lips might be puckered, and you might blow as hard as you pleased, but it was all in vain, as not a note could be heard. Some of us tried to whistle by our fingers, but were unsuccessful.
Communication is had with the upper-world by means of a movable iron rod and a couple of dials, one above and the other below. These form the telegraph. On each dial are printed, in plain letters, the words, “All right,” “Start,” “Faster,” “Slower,” “Stop,” “Less,” “More,” “Bucket is caught,” “Highest corner,” “Stopped,” “Come up all;” and the last is the most pleasing call of the entire number to the laborers below.