The farm land drag, float, or clod crusher is useful under certain conditions on low spots that do not drain properly. Such land must be plowed when the main portion of the field is in proper condition, and the result often is that the low spots are so wet that the ground packs into lumps that an ordinary harrow will not break to pieces. Such lumps roll out between the harrow teeth and remain on top of the ground to interfere with cultivation. The clod crusher then rides over the lumps and grinds them into powder. Unfortunately, clod crushers often are depended on to remedy faulty work on ordinary land that should receive better treatment. Many times the clod crusher is a poor remedy for poor tillage on naturally good land that lacks humus. [Illustration: Figure 140.--Land Float. Clod crushers and land floats belong to the same tribe. Theoretically they are all outlaws, but some practical farmers harbor one or more of them. Wet land, containing considerable clay, sometimes forms into lumps which should be crushed.] As ordinarily made, the land float or clod crusher consists of from five to eight planks, two inches thick and ten or twelve inches wide, spiked together in sawtooth position, the edges of the planks being lapped over each other like clapboards in house siding. The planks are held in place with spikes driven through into the crosspieces. FARM ROLLER Farm rollers are used to firm the soil. Sometimes a seed-bed is worked up so thoroughly that the ground is made too loose so the soil is too open and porous. Seeds to germinate require that the soil grains shall fit up closely against them. Good soil is impregnated with soil moisture, or film moisture as it is often called, because the moisture forms in a film around each little soil grain. In properly prepared soil this film moisture comes in contact with the freshly sown seed. If the temperature is right the seed swells and germination starts. The swelling of the seed brings it in contact with more film moisture attached to other grains of soil so the rootlet grows and pushes out into the soil in search of moisture on its own account. A roller is valuable to press the particles of soil together to bring the freshly sown seeds in direct contact with as many particles of soil as possible. Rolling land is a peculiar operation, the value of which is not always understood. The original idea was to benefit the soil by breaking the lumps. It may be of some benefit on certain soils for this purpose, but the land should always be harrowed after rolling to form a dust mulch to prevent the evaporation of moisture. Land that has been rolled and left overnight shows damp the next morning, which is sufficient proof that moisture is coming to the surface and is being dissipated into the atmosphere. In the so-called humid sections of the country the great problem is to retain moisture. Any farm implement that has a tendency to dissipate soil moisture is a damage to the farmer. Probably nine times