PLOW, an implement originally drawn by horses oxen, etc., used for breaking up or loosening the soil, preparatory to planting or sowing. The plow was the primary implement of civilization. The cultivation of the soil, which began with the invention of the plow, made it possible for men to live in permanent, populous communities, and civilization found a foothold wherever the pastoral tribes of the Stone Age learned the lesson of industry by following the plow. According to an Egyptian legend, ((Osiris taught the way and manner of tillage and good management of the fruits of the earth.? It was undoubtedly in the valley of the Nile, or the Euphrates, that the plow was invented, for in these valleys are found the oldest ruins of agricultural settlements.
The first plow was roughly fashioned from a forked tree. One branch served as the beam, while the other branch was cut off and pointed, and the tail was trimmed to form a handle. Plows of this crude type are pictured on Egyp tian monuments. After bronze tools came into use, it was possible to make a more finished and efficient plow of dressed timbers, and many variations are found in the forms of wooden plows that were used 2,000 to 4,000 years ago. In the prevailing type, a block of wood, with the front end pointed or wedge-shaped, served as the bottom, to which the beam and a single handle were attached. In Latin America, and in many other parts of the world, wooden plows of this form, with iron points and one handle, are in use to this day. The extension of agriculture and civilization in Europe awaited the introduction of iron for plow points, which occurred shortly before the Christian era.
The ancient plow merely stirred or loosened the soil. Modern plows cut a furrow and turn it over so as to cover the sod and weeds, and leave fresh soil on the surface as the seed bed of the crop that is to be planted or sown. Eng lish and American patent records show the evolution, in the past two centuries, of the mod ern form .ofplow. The Colonial plow, which was used in the United States until the begin ning of the 19th century, reflects English ideas in plow-making. The point was of wrought iron, sometimes tipped or edged with steel. The moldboard and all the other parts were of wood, but in some cases the moldboard was covered with sheet iron.
In 1797 Charles Newbold, of New Jersey, patented a cast-iron plow in which the share and moldboard were cast in one piece, but this plow did not prove successful, as the cast-iron point would soon wear off, and farmers could not afford the cost of renewal of so large and expensive a casting. The most practical im provement of thisperiod was made by'Richard B. Chenaworth, of Baltimore, one of the first manufacturers of farm implements in the United States, who patented, in 1813, a cast-iron plow in which the share, moldboard and landside were cast in separate pieces. Jethro Wood, of New York, who took out patents in 1813 and 1819 on improvements in cast-iron plows, has been given credit for important work in the introduction of improved plows, although the main feature of his patent of 1819 was not a practical invention. He never engaged in man
ufacturing, and was unsuccessful in obtaining any income from royalties or licenses under his patents, but he gave his entire life to the work of advocating the use of cast-iron plows.
To James Oliver, of South Bend, Ind., is due the credit for the invention of the chilled plow. He began the manufacture of plows at South Bend, Ind., in 1855. When iron is cast in a chill, that is, in a mold one side of which is a metal vessel filled with water, the sudden cooling of the molten iron in contact with the chill gives the casting a surface as hard as the hardest steel. But the chilled metal was not strong enough to stand the hard usage that a plow receives in the field, and it was impossible to prevent flaws and blow holes in the broad face of a moldboard. After many years of effort, Mr. Oliver mastered the problem. His first success was obtained in chilling the wing or outer end of the mold board, where the friction with the soil is greatest and he ultimately succeeded in this purpose by the use of three inventions. The first consisted in the use of a chill filled with hot water. The heat dried out the moisture of the sand in the mold, and this obviated the flaws and blowholes that were caused by steam, which had been generated when the molten metal was poured into the mold. The next invention was the ventilation of the chill by means of dheckered grooves on its face, which permitted the air and hot gases from the metal to escape from the mold. These two inventions produced a chilled casting which was free from flaws, but moldboards cast in this manner were not strong enough to stand ordinary usage in the field. This last difficulty was overcome by the invention of an annealing process which tempered and strengthened the moldboard without detracting from its wear ing and scouring qualities and made the chilled plows a complete success.
A few of the notable improvements that have been patented by James Oliver are: The cast share, with chilled point and cutting edge, made by a simple process; the share with an upward, coulter-like extension, which fits against the front edge of the moldboard and gives a new vertical cutting edge to the plow when the share is renewed; the curved malleable standard, which brings the beam over the line of resistance of the plow; the simple adjust ment of the beam, which makes the plow bal ance perfectly with two or three horses; the malleable gauge wheel, which regulates the depth of the furrow; and other devices to sim plify and improve the work of the plow.
The next improvement in plows was the sulky or buggy plow, having two wheels and a scat, also a lever for regulating the depth of the share. Then came the gangplow or multi plow, drawn by a tractor instead 'of horses. For such plows the share and moldboard was often impracticable so the disc-plow was in vented, consisting of a circular disced metal share that turned the soil as it rotated. A variety of plows are manufactured for special uses, as for ditching, plowing on a side-hill, for paring sod, or for cultivating particular crops. See AGRICULTURE.