_Spring-toothed harrows_ (Fig. 55). Spring-toothed harrows with their curved spring teeth enter the soil readily, draw moderately easy and pass over obstructions without much difficulty. They are very useful in new land that is full of roots and stumps and also stony land. They pulverize the soil to an average depth. They leave the soil in ridges. The ridges can be leveled by a smoother in the shape of a piece of plank attached to the rear of the harrow. On newly plowed grass land they tend to tear up the sod and leave it on the surface. They also tend to drag out coarse manures when plowed in. The original and more common form of the spring-toothed harrow is a floating harrow when at work. That is, it rests on the points of the teeth and is dragged or floated over the ground. A newer form of spring-toothed harrow, sometimes called the fallow cultivator, is mounted on high wheels and its action is largely controlled by them. This form of harrow is claimed to do much better work than the floating harrow and may in a large measure displace the rolling cutter. The weight of this harrow is entirely taken from the soil except in the wheel tracks, and the entire action is that of pulverizing and lightening the soil. _Spike-toothed harrows_ (Fig. 56). The teeth of these harrows are round, square or diamond-shaped spikes fastened into a wood or iron frame. The teeth are set in a vertical position or are inclined to the rear. These harrows are shallow in their action; they run easily but tend to compact the soil more than the other types and are therefore better adapted to loose soils and to finishing off after the work of the deep cutting harrows. They are also used for covering seeds. [Illustration: FIG. 56.--SPIKE-TOOTHED HARROWS.] [Illustration: FIG. 57.--A COULTER-TOOTHED HARROW.] [Illustration: FIG. 58.--A PLANK HARROW.] _Coulter-toothed harrows._ The coulter-toothed harrows (Fig. 57) have teeth resembling the coulter of a plow twisted or bent into various shapes. The Acme is a good example of this class of harrow. It cuts, turns and pulverizes the surface soil somewhat after the manner of the plow. It prepares a fine mulch and leaves an excellent seed bed. It is an excellent harrow to finish off with after using a rolling cutter. _Chain harrows._ The chain harrow consists of a web of chains linked together. They have a wonderful power for breaking clods and are useful for collecting weeds. They shake the dirt from the weeds and roll them into heaps. Chain harrows tend to compact the soil. _Brush harrows._ The brush harrow is a primitive form made by fastening brush to a long pole. Brush harrows are quite useful for brushing in seed and for pulverizing manure broadcasted on grass lands.