Cahoon seed sowing machine. Cahoon v. Ring, 1 Cliff. 592. Cahoon's seed sower consisted substantially of a hopper to contain the seed and a centrifugal seed distributing wheel which received the seed from the hopper and distributed it centrifugally in the air. Previous to the date of Cahoon's invention, there had been centrifugal seed sowers in which an upright hopper (to contain the seed) was combined with a centrifugal seed discharging wheel arranged to revolve upon a vertical axis or shaft, so that the periphery of discharge of the wheel was in a substantially horizontal plane. In these machines the seed was fed from the hopper to the centrifugal discharging wheel at all sides of the vertical shaft. The practical result was that the seed was delivered from the centrifugal discharging wheel simultaneously at all of its sides and passed to the ground somewhat in the form of an umbrella; the seed never rising above the height of the centrifugal seed discharging wheel from the ground, and being distributed over a narrow strip of but few feet in breath. Cahoon, while retaining the upright seed hopper, the centrifugal discharging wheel and the wheel shaft of the earlier machines, changed the arrangement of the last two members relatively to the hopper so that the shaft was arranged horizontally (instead of being upright), and the periphery of discharge of the centrifugal wheel was in a substantially vertical plane, instead of in a horizontal one. By reason of these changes in arrangement, the mode of operation of the machine was changed, the seed from the upright seed hopper passed to one side of the shaft (of the centrifugal wheel) instead of to all sides of it; the discharge of seed took place at the upper side of the centrifugal discharging wheel, instead of at

all sides of it; and as the seed was thrown off at the upper side of the wheel in a substantially vertical plane (instead of a horizontal one) it rose many feet above the height of the discharger from the ground and was distributed throughout a breadth of sixty feet. In this case, therefore, the change of the relative arrangement of the same old devices (seed hopper, centrifugal discharging wheel, and shaft therefor) was attended with a new mode of operation, and with an improvement in the practical result; and in such a case the change is not a mere change in arrangement but amounts to invention.

§ 13. Invention by Application of an Old Thing to a New Purpose.

While it is undoubtedly true that many applications. of an old thing to a new purpose do not constitute inventions yet there are instances when the change is not a mere application but amounts to invention. Thus, the annealing of articles of metal by first heating them. to a sufficient temperature long enough to permit the molecules to assume the same condition throughout the mass, and by then compelling or permitting them to cool slowly, had been well known for many years, and among such articles were the metallic specula of reflecting telescopes which had been taken hot from the moulds in which they were cast, had been put into a heated oven, and had been permitted to cool slowly therein. With this knowledge in existence, Whitney, on April 25, 1848, patented a process of annealing the chilled cast iron wheels of railway cars. Such wheels are cast in composite moulds; the part of the mould which gives form to the circular tread of the wheel being formed by

a heavy cast iron ring, while the residue of the mould is formed of sand. When molten iron is poured into such a mould the portion which comes in contact with the iron ring of the mould is chilled (and thereby hardened) and cools rapidly, while the hot metal in contact with the residue of the mould (the sand portion) cools slowly because the sand is a much poorer conductor of heat than iron. As iron cools it contracts, and as the rim of the hot wheel is cooled rapidly by contact with the iron portion of the mould, while the residue cools slowly in the sand portion of the mould, the cooling of the metal is rapid at one part of the wheel (the chilled tread) and slow at the residue, and the contraction is unequal; the metal is subjected to internal strains and the body of the wheel tends to break loose from its rim. Even if actual breakage should not take place in cooling, the metal of the wheel is under the action of internal strains so that the wheel is liable to break in use by comparatively slight additional external strains. Attempts had been made to get over the difficulty by modifying the form of the plate or body of the wheel so as to permit it to change its form slightly in contracting, but these attempts had not been successful. According to Whitney's process the wheel is taken hot from the mould. before it has cooled and contracted sufficiently to impair its ultimate strength, it is subjected to heat somewhat below that at which fusion of the iron commences, and is then allowed and compelled to cool slowly in an oven or previously heated chamber. The slow cooling of all the parts of the wheel from the high temperature permits all parts to cool and contract simultaneously and uniformly, and the practical result is that the cooled wheel is as free from internal strains as if it had been

cast in a mould formed wholly of one material, while at the same time the tread of the wheel retains the hardness incident to the rapid chilling of the molten metal by the cast iron portion of the mould. In a suit for infringement under Whitney's patent the case came ultimately upon appeal before the United States Supreme Court (Mowry v. Whitney, 81 U. S. 14 Wall. 620, 20 L. ed. 860) and the court when speaking of chilled car wheels made in the old way said:

"What they needed was (what is substantially described by one of the witnesses) the discovery of the fact that the chilled cast iron, constituting one part of the wheel, could be subjected to heat less than that which would cause fusion, without producing any material effect upon its hardness, while the cooling of the other parts of the wheel could be so prolonged, by applying that heat externally, as to enable all parts to cool without being subjected to the strain attendant on unequal contraction; and, in addition to the discovery, they needed the invention of the process by which it could be practically carried out. Such a discovery and such a process were needed for no other castings. The novelty of the patentee's invention is not therefore disproved by evidence that glass, or speculum metal, or even other iron castings had been annealed and slow-cooled prior to the time when it was made. Of this there is very considerable evidence, both in the testimony of witnesses and printed publications. The specification disclaims invention of annealing iron castings done in the ordinary mode. It claims annealing when applied to cast iron railroad wheels, in the mode or by the process described. It is not, therefore, merely an old contrivance or process applied to a new object, a case of double use.

"A new and previously unknown result is obtained, namely, the relief of the plate of the wheels from inherent strain without impairing the chilled tread; a result which, though anxiously sought, had not been obtained before Whitney's invention."

This example shows that when an old thing (in this case a process) is so applied as to obtain a new result, (the production of a chilled car wheel free from internal strains) the change or thing done is not a mere application of an old process to a new or different thing, but is an invention.

A similar instance of invention in the application of an old thing is found in the case of the stove regulator of Foote, described in his patent of May 26, 1842. The apparatus as a whole consisted of a stove with its draft valve (for the admission of air) connected by two levers with two expansion rods of sheet brass; screws and nuts also were used to adjust the expansion rods. The metal of the rods, being brass, expanded and contracted to a greater extent than the metal of the stove, which was iron; and by reason of the difference in extent of movement of the rods and metal of the stove, the draft valve was closed and opened. The patent was infringed and there was a trial by jury, with a verdict for the plaintiff. Various alleged anticipations by similar apparatus were set up, such prior devices showing the application by machinery of the unequal expansion and contraction of two different metals under the same degree of heat to various purposes, such as regulating the temperature of an apartment, or of a hot-house, or of a water, oil or alkaline bath, by the contemporaneous admission of warm and discharge of cold air or fluid effected through the action of the regulator placed in the medium whose tem