Did you ever notice how big boulders in a field are frequently sunk into the ground as if dropped from a great height? It is the earthworms that help sink them in the course of their soil-making. They like the moist shelter of the stones and burrow under them. Finally the weight of the stones crushes the burrows, and so the stones sink down.
Poor soil, as every boy knows, is a poor place to look for fishworms. But you have noticed that the mounds the worm throws up on such soil are larger than those on rich soil. The reason is that the soil, being less nutritious, the worm must eat more of it and, in so doing, pulverizes and fertilizes it. But a menu of earth alone not being to the earthworm's liking, undesirable regions have fewer of these farmers working underground; and this, for the same reason that these regions are sparsely settled on the surface--it is so hard to make a living.
So the earthworms may be said to have a decided taste in landscape. They don't care for desert scenery like Gerome's picture of the lion's big front yard,[9] but they are very fond of orchards where the soil is rich and leaves are plenty. The pathways artists are fond of putting in landscapes would also probably attract the eyes of earthworms--if they had any, for the worms prefer soil a little packed, as it is in pathways, because it makes more substantial burrows. And, singularly enough, the worms also like most the very thing that the artist emphasizes to lead the eye into his picture--the border lines that _define_ the path. It is along the edges of a pathway that you find most worms.
[9] "The Two Majesties." This painting, by a great French realist, shows a lion getting home rather late, after his night out, stopping for a look at the rising sun; a thing with which, owing to his habits, he is not very familiar.
[Illustration: _Painted by F. O. Sylvester._
Two features common to both these pictures--the trees and the pathways--appeal to earthworms as well as artists, for reasons you have learned in this chapter.]
The earthworm, in addition to working over and fertilizing the soil already made, actually helps make soil out of rock. He does this in two ways: (1) With acids--for, like the Little Old Man of the Rock, he is a chemist; (2) by grinding up rock in a little mill he always carries with him.