Sometimes when a geologist picks up a pebble and looks at it a moment he can hear the roar of mountain torrents and of lowland streams in flood. If the pebble is round it shows that it has been carried far and rolled about by streams. If it has pits in it this shows that its water journeys were rough, because such pits are made by knocking against other pebbles and sharp stones in the struggle and confusion of the rushing waters. You see these little dots are a kind of shorthand, for we pebbles are stenographers too!
THE PERCHED BOULDER IN BRONX PARK
This is one of the interesting things to be seen when you visit Bronx Park in New York City. Of course, you know how that old boulder got there, and how he drew those straight lines in the rock-bed beneath, but many visitors to the park do not.
HOW PEBBLES TELL OF THEIR TRAVELS
Other great stories in small space are told on glacial pebbles. Scientific men can often tell from the look of a pebble whether it was shaped by rivers, by the sea, by the sand blasts of desert winds, or by the glaciers. Not only that, but, if it is a glaciated pebble, on what part of the glacier it was carried; whether in the middle of its back, or on the sides, like the passengers in an Irish jaunting-car; or whether it rode underneath, like a tramp stealing a ride on the bumpers. The stones in the middle of the glacier's back naturally keep their sharp edges longer than stones on the side, ground as the side stones are by the moving ice mass against the mountain walls. And the stones on both top and sides would lose less of their edges than the stones underneath the ice.
From Norton's "Elements of Geology." By permission of Ginn and Company
ONE PEBBLE IN ITS TIME PLAYS MANY PARTS
Here are pebbles faceted in different ways by glaciers. No. 1 has six facets. No. 4, originally a rounded river pebble, has been rubbed down to one flat face. Nos. 3 and 5 are battered little travellers faceted on one side only. Notice how No. 5 got his face scratched just as I did.