There are different well-known devices, any one of which may be adapted to effect a given result, according to the judgment of the constructor. The mere substitution of one of these for another does not belong to the subject of invention, but of construction. (Foster v. Moore, 1 Curt., 291.)

By equivalents in machinery is usually meant the mere substitution of one mechanical power for another, or one obvious and customary mode for another, to effect a like result. (Smith v. Downing, 1 Fish., 64.) The term "equivalents" has two meanings, as used in patent cases. The one relates to the results that are produced, and the other to the mechanism by which these results are produced. (Johnson v. Root, 1 Fish., 352.)

A mechanical equivalent, as generally understood, is when one thing may be adopted instead of another, by a person skilled in the art, from his knowledge of the art. (Ib.)

By an "equivalent" is meant something that does the same thing in substantially the same way. (Cahoon v. Ring, 1 Fish., 397.)

When a party has discovered a result, as well as the machinery that produces it, he has a right to invoke the doctrine of equivalents in reference to infringers. (Singer v. Walmsley, 1 Fish., 558.)

But where he is only the original inventor of a device, he can only recover against an infringer, if he shows that he has substantially copied his invention. In other words, being an improver himself, he cannot invoke the doctrine of equivalents to help him. (Ib.)

Where a patent is granted for a composition made of several ingredients, it covers and embraces known equiv

alents of each of the ingredients. (Matthews v. Skates, 1 Fish., 602.)

An equivalent of any substance is another substance having similar properties and producing substantially the same effect. (Ib.)

An equivalent device is such as a mechanic of ordinary skill in the construction of similar machinery, having the plaintiff's specification and machine before him, could substitute in the place of the mechanism described, and without the exercise of the inventive faculties. (Burden v. Corning, 2 Fish., 477.)

In the case of Foster v. Moore, Mr. Justice Curtis charged the jury as follows: "The term 'equivalent,' gentlemen, has two meanings, as used in this class of cases. The one relates to the results that are produced, and the other to the mechanism by which those results are produced. Two things may be equivalent, that is, the one equivalent to the other, as producing the same result, when they are not the same mechanical means. Mechanical equivalents are spoken of as different from equivalents that produce the same result. A mechanical equivalent, I suppose, as generally understood, is where the one may be adopted instead of the other, by a person skilled in the art, from his knowledge of the art. Thus an instrumentality is used as a mechanism. You wish to produce a pressure downward; well, it can be done by a spring or it can be done by a weight. A machine is presented to a person conversant with machines. He sees that the force applied downward in the one before him is by weight; from a knowledge of his art he can pass at once to another force-the spring to press it downward; and these are mechanical equivalents. But,

gentlemen, there may be equivalents in producing the same results, each of which is an independent matter of invention, and in that sense they are not mechanical equivalents. To illustrate my meaning, suppose in early days the problem was to get water from a well to the surface of the earth: one man takes a rope made of grass and draws up a pail of water; another would see that, as a mechanical equivalent, a rope of hemp would accomplish the same result. But suppose that another person comes and for the first time invents a pump: that is equivalent in the result to bringing the water to the surface of the ground; in that respect it is equivalent, as producing that result, to hauling it up by a rope, but it is not mechanically equivalent; it brings into operation, as you know, different powers and forces, and would require invention to introduce it. (1 Curtis C. C., 279.)

24. MECHANICAL SKILL.-There must be embodied in the invention, over and beyond the skill of the mechanic, that inventive element of the mind which is to be found in every invention that is the proper subject of a patent. (Tatham v. Le Roy, 2 Blatchf., 488.)

Mere mechanical skill can never rise to the sphere of invention. The latter involves higher thought and brings into activity a different faculty. Their domains are distinct. The line which separates them is sometimes difficult to trace; nevertheless, in the eye of the law, it always subsists. (Blandy v. Griffith, 3 Fish., 609.)

It is difficult to determine where ordinary mechanical skill ends and invention begins. The best practical principle is, that where the combination of known elements produces new and useful results to the public not before

attained, then the person who discovers and applies the combination is an inventor, within the true intent and meaning of the patent law. (Smith ex parte, MS. Appeal Cases, D. C., 1860.)

25. DISCOVERY.-Discovery is synonymous with invention, under the Constitution and laws of the United States respecting patents. (Kemper ex parte, MS. Appeal Cases, D. C., 1841.)

A patent cannot be granted for the discovery of a fact which long before existed; there is no invention, nothing contrived or produced. (Ib.)

In its naked and ordinary sense a discovery is not patentable. It is only when the explorer has gone beyond the mere domain of discovery, and has laid hold of the new principle, force, or law, and connected it with some particular medium or mechanical contrivance, by which, or through which, it acts on the material world, that he can secure the exclusive control of it under the patent laws. He then controls the discovery through the means by which he has brought it into practical action, or their equivalent, and it is then an invention, although it embraces a discovery. (Morton v. New York Eye Infirmary, 2 Fish., 320.)

A discovery may be the soul of an invention, but it cannot be the subject of the exclusive control of the patentee, or the patent law, until it inhabits a body, no more than can a disembodied spirit be subjected to the control of human law. (Ib.)

He who has discovered some new element or property of matter may secure to himself the ownership of his discovery, but the mental conception must have been embodied in some mechanical device or some process

of art. The patent must be for a thing, not for an idea merely. (Vide supra, p. 219; Detmold v. Reeves, 1 Fish., 127.)

The discovery of a fact, that a given natural substance will, in appropriate methods of administration, produce a particular physiological or pathological effect on the human body, is not a thing patentable under any existing statute. (Morton's Anæsthetic Patent, 8 Opinions Attorneys General, 272.)

A new process is generally the result of discovery-a machine of invention. (Corning v. Burden, 15 How., 267.) 26. NOVELTY.-As to the novelty of the invention, the rule is that it must be new as to all the world; not the abstract discovery, but the thing invented; not the new secret principle, but the manufacture resulting from it. (Whitney v. Emmett, Bald., 309.)

The thing itself which is patented must be new, not merely the purpose to which it is applied. (Bean v. Smallwood, 2 Story, 411.)

The question is whether the thing has been known before. In case of a machine, whether it has been substantially constructed before; in case of an improvement of a machine, whether that improvement has ever been applied to such a machine before, or whether it is substantially a new combination. (Earle v. Sawyer, 4 Mason, 6, 7.)

The question is not whether the invention is better or worse than its predecessor, but whether it is new and useful, and different from anything before used or known. (Blandy v. Griffith, 3 Fish., 609.)

The law does not require any degree of utility; it does not exact that the subject of the patent shall be better