Yet some day he may, all of a sudden, take a jump! Boulders do that sometimes, as you will see before you have finished this chapter.
ON THE NORTH END OF THE WORLD
Some of the boulders seem to have belonged to Alpine Clubs, for you find them away up on mountain sides; some of them as high as 6,000 feet—that's over a mile you know—above the level of the sea. And often these boulders are not of the same material as the huge pieces of broken rock that fall from the neighboring mountain walls. Moreover the blocks of stone from the mountain are angular; they are not nicely rounded off as are boulders and pebbles. It's that way all over the north end of the world as far south as the Ohio in this country and the Alps in Europe.
WOULDN'T IT MAKE YOU NERVOUS, TOO?
This picture is from a story about a little boy who had to cross a field full of big, dark boulders like this at night, and how nervous it made him.
But there's one place in which you never will find boulders, and that's in a country where there are caves of any considerable size. Neither will you find such caves where there are boulders.
Why shouldn't the caves and the boulders live happily together just like other people? The answer is simple. The glaciers of the Ice Age, with their enormous weight, crushed in the roofs of caves in every region over which they flowed; and it was these same glaciers that left the boulders. Since the glaciers went away the underground rivers that hollow out the caves have not had time to make new ones. It takes ages and ages to make a nice big cave.
II. The Train of Thought
These widely scattered boulders furnished the students of the subject with the very best evidence that there was once an Ice Age. First, the geologists noticed, just as the Indians did, that the boulders were of a different kind of rock from that of the regions in which they were found. Up in Wisconsin, running southwest from Waterloo is a train (as it is called) of boulders sixty miles long. The boulders are of a very hard rock called quartzite, while all the rock deposits in that region are of limestone or sandstone.