Jethro Wood, Inventor of the Modern Plow. / A Brief Account of His Life, Services, and Trials; Together with Facts Subsequent to his Death, and Incident to His Great Invention

by Frank Gilbert

Jethro Wood took out two plow patents, and those who wish to belittle his work, descant upon the first as if it were his only claim to credit. That first patent was issued in 1814. It fell far short of satisfying the patentee’s ambition. The plows made under it must have been a great improvement on any then in use, for although he abandoned it almost from the first, a great many of them were sold during the period between the first and the second patents. The second patent dates from 1819. The natal day of the modern plow may be fairly set down as September 1, 1819. The original specifications in this plow deserve to be given in full, and may well be inserted in this connection. The document was the handiwork of Mr. Wood himself, and runs thus:

“The Schedule referred to in these Letters Patent, and making part of the same, containing a description in the words of the said Jethro Wood himself of his improvement in the construction of Ploughs.

“Considering the manifold errors and defects in the construction of Ploughs, and the inconveniences experienced in the use of them, the petitioner and inventor hath applied the powers of his mind to the improvement of this noble utensil, and produced a Plough so far superior to those in common use, that he asks an exclusive privilege for the same from the government of his country.

“The principal matters for which he solicits Letters Patent, he now reduces to writing, and explains in words and sentences as appropriate and significant as he possibly can. But, being perfectly aware of the feebleness and insufficiency of language to convey precise and adequate ideas of complicated forms and proportions, the said Jethro Wood annexes to these presents, a delineation upon paper of his said new and improved Plough, with full and explanatory notes; urging with earnestness and respect that the delineation and notes may be considered as a part of this communication. The said petitioner and inventor also, being perfectly convinced, as a practical man, that a model of his inventions and improvements will convey and preserve the most exact and durable impressions of the matters to which he lays claim, he sends herewith a model of the due form and proportion of each, as a just exhibition of his principle and of its application to the construction and improvement of the Plough, requesting that the same may be kept in the Patent Office, as a perpetual memorial of the invention and its use.

“In the first place, the said Jethro Wood claims an exclusive privilege for constructing the part of the Plough, heretofore, and to this day, generally called the mould-board, in the manner hereinafter mentioned. This mould-board may be termed a plano-curvilinear figure, not defined nor described in any of the elementary books of geometry or mathematics. But an idea may be conceived of it thus:

“The land-side of the Plough, measuring from the point of the mould-board, is two feet and two inches long. It is a strait-lined surface, from four to five and one-half inches wide, and half an inch thick. Its more particular description will be hereinafterwards given. It is sufficient to observe here, that of the twenty-six inches of length on the land-side, eighteen inches belong to the part of the Plough strictly called the land-side, and eight inches to the mould-board. The part of the mould-board comprehended by this space of eight inches is very important, affording weight and strength and substance to the Plough; enabling it the better to sustain the cutting-edge for separating and elevating the soil or sward, and likewise the standard for connecting the mould-board with the beam, as will hereinafter be described more at large.

“The figure of the mould-board, as observed from the furrow-side, is a sort of irregular pentagon, or five-sided plane, though curved and inclined in a peculiar manner. Its two lower sides touch the ground, or are intended to do so, while the three other sides enter into the composition of the oblique, or slanting mould-board, over-hanging behind, vertical midway, and projecting forward. The angle of the mould-board, as it departs from the foremost point of, or at, the land-side, is about forty-two degrees, and the length of it, or, in other words, of the first side, is eleven inches. The line of the next, or the second side, is nearly, but not exactly parallel with the before-mentioned right-lined land-side, for it widens or diverges from the angle at which the first and second sides join towards its posterior or hindermost point, as much as one inch. Hence, the distance from the hindermost point of the mould-board, at the angle of the second and third sides, directly across to the land-side, is one inch more than it is from the angle of the first and second sides, directly across. The length of this, the second side, is eight inches. The next side, or what is here denominated the third side, leaves the ground or furrow in a slanting direction backward, and with an over-hanging curve, exceeding the perpendicular outwards from three to six inches, according to the size of the Plough. The length of this third side is fourteen inches and one-half. The fourth side of this mould-board is horizontal, or nearly so, extending from the uppermost point of the third side, to the fore part, or pitch, eighteen inches. The fifth, or last side, descends or slopes from the last mentioned mark, spot, or pitch, to the place of beginning at the low and fore point of the mould-board, where it joins the land-side. Its length is thirteen inches.

“Besides these properties and proportions of his mould-board, the said Jethro Wood now explains other properties which it possesses, and by which it may be and is distinguished from every other invented thing. The peculiar curve has been compared to that of the screw auger; and it has been likened to the prow of a ship. Neither of these similitudes conveys the fair and proper notion of the invention.

“The mould-board, which the said Jethro Wood claims as his own, and which is the result of profound reflection and of numberless experiments, is a sort of plano-curvilinear surface, as herein-before stated, having the following bearings and relations: A right line, drawn by a chalked string or cord, or by a straight rule, diagonally or obliquely upwards and backwards from a point two inches and a half inch above the tip or extremity of the mould-board to the angle where the third and fourth sides of the mould-board join, touches the surface the whole distance, in an even and uniform application, and leaves no sinking, depression, hole, cavity, rising, lump, or protuberance, in any part of the distance. So, at a distance half way between the diagonal line just described, and the angle between the first and second sides, a line drawn parallel to the diagonal line already mentioned will receive the chalked string or cord, or the straight rule, as on an uniform and even surface without the smallest bend, sinuosity, or bunch, whereby earth might adhere to the mould-board, and impede the motion and progress of the Plough, under, through and along the soil.

“In like manner, if a point be taken one inch behind the angle connecting the second and third sides, and a perpendicular be raised upon it, that perpendicular will coincide with the vertical portion of the mould-board in that place; or, in other words, if a plumb line be let fall so as to reach a point one inch behind the last mentioned angle, then such a plumb line will hang parallel with the mould-board the whole way; the line of the mould-board there, neither projecting nor receding but being both a right line and a perpendicular line.