There are numerous other kinds of plows used for special purposes. such as trench or ditching plows. which are made on the same principle as the common plow, but larger and stronger, so as to bring up a portion of the subsoil to the sur face: or subsoil plows, which have no mold-board, and merely stir and break lip the subsoil. thus facilitating drainage. These plows are not used so much as formerly. There are also double mold-board plows, which are merely common plows with a mold-board on each side, em ',toyed for water-furrowing, etc.; the hillside or swivel plow, which is provided with a reversible mold-board. so that the team may xvalk in the opposite direction, but always place the furrow against the one previously turned. .1nother special form of plow is the double-furrow or gang plow (Fig. 4). which consists of an iron frame, usually mounted on a wheel or wheels, carrying two or more plows. one set a little to the rear of the other. and at the distance it is de sired the width of the furrow• should be. The sulky plow (Fig. 5) has also come into exten sive use, the object of stud' being to lessen friction and reduce the labor of the plowman. The draught of such plows, however, was found by Sanborn to be not materially less than that of the ordinary swing plow. The first patent for sulky plows in ..1merica was granted to 11. llrow•n in 1844. but practical plows of this type were not made until about 1804, and the manufacture of such plows is still in a state of tWOIntion, al though ionnerous forms are found on the market. The disk plow (Fig. 0), which is a comparatively recent invention, is attracting wide attention on account of its effective work tinder certain con ditions. The principal feature of this plow in its more perfect form is a tempered steel disk 25 to 30 inches in diameter, and usually set at an angle to the furrow• and to the surface so as to turn and pulverize the soil. It is kept from clogging and assisted in pulverizing the soil by an adjustable scraper. The disk is carried by a steel framework mounted on wheels and provided with a scat for the driver and levers for control and adjustment of the plow.
The idea of the use of engines and machinery to plow the ground seems to have originated with David and Thomas Wildgosse in. 1618, but the motive power they proposed to use is not made clear. Francis :Moore in 1769 first attempted to use the steam-engine for this pur pose. The history of practical steam plowing dates from the invention of Fowler, assisted by Smith, in 1854. The inventions along this line have included plans for engines traveling over the surface of the ground, drawing plows or other cultivating implements along with them: engines working on tramways, and drawing im plements after them; engines moving along oppo site headlands, and working implements be tween them by means of wire ropes and station ary engines driving implements also by means, of wire ropes. The steam plows used most widely in England belong to two classes—double-engine and single-engine or 'direct' and `round-about' (Figs. 7 and S). Gang plows carried on wheels are usually employed in these systems, the plows being in two series facing in opposite directions and so arranged that when one series is in opera tion the other is elevated above the soil. The steam plows used in America are of the gang class drawn by a traction engine as shown in Fig. 9. Attention of American inven tors has been directed mainly toward develop ing a cheap, light, and durable engine of sutli The time and manner of plowing will be de termined by the special object to be attained.
In soils more or less impervious to water it is advisable to plow to different depths at different seasons of the year in order to prevent the forma tion of hardpan, which occurs when plowing to the same depth for several seasons, due to the cient traction and adapted to different kinds of land. On the Western wheat ranches there has, according to Taylor, been "developed a special form of engine for plowing, harvesting, and sim ilar work. These engines have assumed a tri cycle form, the weight of the boiler and engine pressure of the plow and the trampling of the teams. If the soil is very pervious it is some times desirable to promote this formation of hardpan to arrest a too rapid percolation of water. Plowing promotes ai;ration of the soil and nitrification (q.v.), and otherwise improves resting on two very high, wide tread whoe]s with a third wheel of castor type in front for easy steer ing. A high-pressure, force-draught boiler is used, and small, high-speed engines, developing from 40 to 80 horse-power. Such engines draw from 12 to 18 twelve-inch plows, and turn over 25 to 40 acres per day." A system using electricity on the trolley plan has been introduced in Germany with some success. It is claimed for the better systems of steam and electric plowing that they are cheaper and more efficient than the ordinary methods. This may be true where horses and feed are expensive, fuel cheap, and lands level and otherwise well suited to these systems; hut that it is universally true remains to he demon strated.
the physical and chemical condition of soils, re sulting in increased productiveness. A deep tilled layer of soil is desirable, but this should he brought about gradually, since the plowing should not be so deep as to bring up raw sub soil. Plowing to a greater depth than G or 7 inches is rarely desirable. The time and man ner of plowing will be determined by climatic conditions, character of soil, and kind of crop to be raised. Sod may be plowed wetter than stubble land. In midsummer and fall deep plow ing is desirable, in early spring rather shallow plowing is usually best. Manures and similar material should not be turned under deeply in the spring. If there is danger of too rapid evap oration, surface tillage should follow very closely after plowing. Fall-plowed land should general ly" br left rough. Unless the s•dl has very good natural drainage the plowed land should have 'pen furrows from 10 to 15 paces apart. Thor ough and deep plowing is most economically per formd with a large sulky plow %vith three or more horses (Fig. 5), except when the fields are small.
meat as counsel for those of his own faith, Bishop Bonner being one. llis present reputation, how ever, rests chiefly on a series of reports of trials, Lea COMen tarirs. etc. ( London. 1571 ; trans., Dub lin, 1792: London, 1816), written in law French, made by him and extending over the entire period of his connection with the bar. They are val uable as a careful and clear record of early Consult: Roberts, Fertility of the Land (New York. 1897) ; Brooks, Agriculture, vol. i. (Spring field, 1901) ; King, Physics of Agriculture (Mad ison, 1901) ; Ardrey, American Agricultural Im plements (Chicago, 1S94) ; Missouri Experiment Station Bulletin No. 32. Plows and Plowing (Columbia, 1888) ; Utah Experiment Station Bulletin No. 2, Plow Trials (Logan, 1S90) ; United States Census Report 1860, volume on Agriculture.