First of all let us consider the ways of the ant (as the Bible tells us to). The ant's work may be said to take up where the earthworm leaves off. Mr. Earthworm, as we have seen, is a little fastidious about the kind of land he tills. Among other things, he is inclined to avoid sandy soil, while the ants will be found piling up their pretty cones of sand or clay as well as of black earth. And in some soils the ants do more important work than the worm that helped make Mr. Darwin famous. In the course of a single year they may bring fresh soil to the surface to the average depth of a quarter of an inch over many square miles. This not only helps to keep the farmer's fields fertile by adding fresh, unused earth, but enriches them by burying the vegetation--such as leaves and twigs and branches broken from dead trees by storms--so that it decays. This burying of vegetation is the very thing the good farmer does when he spreads his fields with manure from the barnyard, or when he ploughs under the stubble. [Illustration: A HEAP OF GRIST FROM AN ANT SOIL MILL Something of an ant-hill, isn't it? It is a foot high and measures nearly three feet across. You will find such ant hills in the Arkansas Valley in Colorado, where the photograph of this one was taken.] Ants are very glad to do this for the farmer because it isn't any extra trouble for them. Their little heaps of fresh earth are thrown out in connection with the building of their homes. The mining ants dig galleries in clay, building pillars to support the work and covering them with thatches of grass. The red and yellow field ants are the masons. They first raise pillars and then construct arches between them, covering these arches with the loose piles of soil which we know as ant-hills. The carpenter-ants bore their cells in the dead limbs of trees, and the wood dust they make from them hurries on the process of returning these dead limbs to the soil. One kind of carpenter-ant covers its walls with a mixture of sawdust, earth, and spiders' webs. An ant in Australia builds its home of leaves fastened together with a kind of saliva. One kind of ant, whose calling card among scientific people is Formica fusca,[12] adds new stories to old houses as the colony grows; much as in the growth of cities and hamlets the buildings grow taller with the growth of the town. Just as men do, such ants first build the side walls and then the ceilings. As if these ants are working under contract and must get their job done by a certain time, two groups are employed on the ceiling at the same time, each group working toward the other from the opposite wall and meeting in the middle.