[to be continued.]
[THE ROCKS.]
BY CHARLES BARNARD.
THE ROCKS TELLING THEIR STORY.
Not long ago I saw some men at work in a stone quarry on Second Avenue, at the corner of Seventieth Street, New York. In this part of the city there are many empty lots not yet built upon. These vacant squares are in some places covered with great masses of rough rocks, that must be cleared away before the houses can be built. So it happens there are stone quarries right in the midst of the city. In talking to you about the sea, you may remember I told you the world is like a great picture-book. Here is one of the leaves lying wide open, where we may read a strange old story. Those of you who live in New York can go up to Seventieth Street and see it; but the men are busy tearing it down, and before you get there, there may be nothing left but a fine row of cellars or a block of houses. Many of you can not visit New York, so I carried my camera to the place, and took a photograph of the rocky wall. The engraver has made a picture from my photograph, and here you can see it. At the left you can look down Seventieth Street, and see part of the rocky hill on the next block. On top is an old shanty, a tree or two, and a tumble-down fence. Directly in front is the solid wall of stone, just as it has lain there for perhaps tens of thousands of years. In the foreground are the broken fragments of rock that have been torn down by the blasts. One of the quarry-men looked up from his work just as I set up my camera, and got nicely caught in the picture.
You must study these rocks. See how they are split into thin sheets and layers. The rocky wall is full of horizontal seams. It looks as if made of thin layers laid one over the other. The middle part of the rock, that is in the shadow of the overhanging layers, is divided into very fine layers, so close together it is hard to tell them apart, yet you can see by the broken edge against the sky that all the rocky pile is in sheets and layers one above the other.
I carried some of the small pieces home, and rubbed them together over a sheet of paper, and soon had a small heap of black and white dust. Here we have two things about these rocks. The picture shows you the rock is arranged in layers. Rubbing the pieces together showed that it was made up of fine dust that when wet would resemble mud or wet sand. These things plainly point to the water. The rock must have come from the sea.
The rain and the frost may have begun the work. The rain wet some old rocks, and the cold turned the water to ice, and the ice worked its thin fingers into every crack, and broke off millions of small pieces. The spring torrents swept this dust into the streams, and these carried it to the sea that then covered all this part of the country. Perhaps it was the surf beating on some ancient shore that ground up the rocks; but of this we can not be so sure as we may be concerning some other rocks we shall see presently. One thing is pretty plain. The loose dust or mud was swept hither and thither by the tides and currents. Very likely the moon arranged all these sheets of stone. The tides rose and fell as the moon swung round the world. Each tide carried up some of the soft glittering and silvery mud, and left it on the shore to dry in the sun. The next tide brought a little more, and laid it over the first sheet. In this way, for perhaps hundreds of years, the moon bid the sea spread carpets of mud and soft sand one over the other upon its floor. Under the shadow of the overhanging part of the rock it seems to be of quite a different kind. Something happened, and the tides and currents brought a different kind of material.