The phosphates (that is, phosphorus) are the only large items of expense, and in a large measure this may be lessened by raising live stock, for which high prices can be obtained either as meat or dairy products, and returning the manure, which contains a large amount of phosphate, to the soil. If all the waste animal products could be returned to the land, Professor Van Hise says, three-fourths of the phosphorus would be replaced. All animal products are rich in phosphates. The packing houses manufacture large quantities from the bones and blood of animals. The garbage of cities, when reduced to powder, yields large returns in phosphorus. It is said that if the sewage of cities, which in this country is often turned into rivers and streams, polluting them and causing disease, was reduced to commercial fertilizer, it would supply the equivalent of from six to nine pounds of rock phosphate per year for every acre of cultivated land in the United States. And this valuable product is now totally lost, and worse than lost, since it menaces the life and health of great numbers of our people. There still remain to be considered the rock phosphates, the form in which phosphorus is found in separate deposits. The only large deposits that have been used are in Florida, South Carolina, and Tennessee, and from them about two and a quarter million tons were mined in 1907. Unfortunately, however, there is no law that prevents its export from this country, and almost half of this found its way to Europe, where it is eagerly sought at high prices. Within a short time valuable phosphate beds, more extensive than any before known to exist in this country, have been discovered in Utah, Wyoming, and Idaho. Professor Van Hise, who is one of the highest authorities on the subject, says of these deposits that with the exception of our coal and iron lands, they are our most precious mineral possession; that every ounce should be saved for the time which is coming when the population will have outgrown the capacity of the land, and means of increasing its fertility in order to prevent famine will be sought from every possible source. The other great waste of the soil is by erosion, or the wearing away of the soil by stream-flow. We can all see this in a small way by wandering along the shore of any swift-running stream and noticing how the banks are worn away, and what deep gullies and ravines are cut into them by the water running down from the fields above. Another way in which we can observe the effect of this waste is by noticing the muddy yellow color of streams during floods and after heavy rains, and comparing it with the clear blue of the same stream at ordinary times.