Professor Roberts has suggested $250 per year as a conservative estimate of the value of the manure produced during seven winter months on a farm carrying four horses, twenty cows, fifty sheep and ten pigs. The estimated value may be made much higher in cases where farmers are willing to use thought and labor in preparation and preservation of home-made manures. =Solid Manure and Liquid Manure.=--The urine is the most valuable portion of the excretion of animals, according to the tables of the agricultural chemists. It is especially rich in nitrogen, and, hence, its strong odor under fermentation. It is also rich in potash. Its place is on the manure heap, not in a ditch leading to a brook. If it collects in quantities beyond the absorbing power of the manure pile, it should go on the compost heap or else be diluted and at once put upon the land. =When to Fertilize.=--The land is a good bank in which to deposit money in the form of manure; but there are certain portions of the year when the land bank declares no dividends. It is safe to put manure upon an unfrozen soil at any time, but the best, the quickest, and the largest results are obtained by manuring during the growing season, preferably just before planting the crop. Small applications, often repeated, are preferable to large, though rare, applications. Plants, like animals, consume small amounts of food each day, and cannot take a year's food at a single meal. =Humus.=--Humus, often referred to by agricultural writers, is a name for decaying organic matter in the soil. Green crops turned under, grass roots, stubble, leaves, long manure, etc., form humus. The term is a comprehensive one. Humus is a dark-colored substance, abundant in all rich ground. A lump of manure that has been lying in the ground for a year or two has become, practically, a mass of humus. =Minute Soil Workers.=--In all good soils there are myriads of small organisms, whose duty is to destroy organic matter and convert it into soil, or into humus, or into plant food. This explains the superiority of good, moist soil as compared to coal ashes for making compost heaps. Coal ashes are worth sifting, if the work can be done automatically; that is, by simply pouring the ashes upon a sloping wire screen. The coarse portion of the ashes, if not worth reburning, will at least make good walks, drives or road beds, while the fine portions make excellent absorbents to put under hen roosts. [Illustration: Some of the many Forms of Bacteria. (Magnified).]