modes of its embodiment in a concrete invention may be numerous and in appearance very different from each other." Robinson on Patents, § 485. The invention, of course, must be described and the mode of putting it to practical use, but the claims measure the invention. They may be explained and illustrated by the description. They cannot be enlarged by it. Yale Lock Co. v. Greenleaf, 117 U. S. 554. Snow v. Lake Shore &c. Railway Co., 121 U. S. 617, is a case where a claim was limited by a description of the device, with reference to drawings. The court, in rejecting the contention that the description of the particular device was to be taken as a mere recommendation of the patentee of the manner in which he contemplated to arrange the parts of his machine, said there was nothing in the context to indicate that the patentee contemplated any alternative for the arrangement of the parts of the device. Therein the description is distinguished from the description in the Liddell patent. Liddell was explicit in the declaration that there might be alternatives for the device described and illustrated by him. He was explicit in saying that in place of the device for controlling the movement of the forming plate relatively to the cylinder that the plate might "be moved or operated by any other suitable means."

This court said in Cimiotti Unhairing Company v. American Fur Refining Company, supra: "In making his claim the inventor is at liberty to choose his own form of expression, and while the courts may construe the same in view of the specifications and the state of the art, they may not add to or detract from the claim." See also Howe Machine Co. v. National Needle Co., 134 U. S. 388, 394.

The discussion thus far brings us to two propositions: that infringement is not averted merely because the machine alleged to infringe may be differentiated from the patented machine, even though the invention embodied in the latter be not primary; and, second, that the description does not necessarily limit the claims. It is probably not contended

abstractly by the Continental Company that the description necessarily limits the claims, but only in the case at bar as following from the first proposition, that is, as resulting from the alleged narrow character of the Liddell invention. A few words more may be necessary to develop fully the contention. Counsel separates the claims of the Liddell machine into divisions, and says that the fourth division of the claimed mechanism in each of the three claims alleged to be infringed is in exactly the same words, which words are: "Operating means for the forming plate, adapted to cause the said plate to oscillate about its rear edge upon the surface of the cylinder during the rotary movement of said cylinder." And it is argued that neither claim designates "operating means," either by names or by reference letters or numerals, and recourse must therefore be had to the descriptive part of the specification to ascertain what "operating means" are meant, and then construe the claim as calling for those "operating means or their equivalents. The other way, it is said, is to ignore the descriptive part of the specification "and to construe the claim as being satisfied by any 'operating means' which can perform the particular function designated in the claim." Under the second method, it is insisted, identity of function constitutes infringement. Under the first method identity of function must be accompanied by substantial identity of character and substantial identity of mode of operation in order to constitute that result. The second method was adopted, it is urged, by the Circuit Court, and led it into the error of deciding that "Liddell's alleged invention covers every method of combining the rotary cylinder with the forming plate to oscillate about its rear edge on the surface of the cylinder, and the claims are as broad as the invention."

It may be well before considering these contentions to refer again to the view which the Circuit Court and the Circuit Court of Appeals had of Liddell's patent. The Circuit Court said that the "pith" of the invention "is the combination of the rotary cylinder with means for operating the forming plate

in connection therewith, limited, however, to means which cause the plate to oscillate about its rear edge on the surface thereof," and distinguished the invention from the prior art, as follows: "Aside from the cylinder and the forming plate oscillating about its rear edge everything in these claims [the claims of the patent] is necessarily old in the arts." It was this peculiar feature of novelty, it was said, which clearly distinguished it from all that went before it. This conclusion was in effect affirmed by the Circuit Court of Appeals. The latter court said that the folding of the bottoms of S. O. S. paper bags had been accomplished in the prior art "both by a folding plate reciprocating upon a plane, and by the operation of fingers upon a cylinder. The folding plate and the cylinder had never been combined. The complainant urges with much probability that the reason why they had not been combined lay in the difficulty of operating a pivoted folding form upon the surface of a cylinder. Two circles external to each can be in contact at but one point, while, in order that the folding plate may operate, its end, as it moves upon a pivot, must remain for some distance in contact with the surface of the revolving cylinder. The problem may be solved by causing the pivot or axis of the folding plate to yield away from the cylinder, or by causing the surface of the cylinder to be depressed away from the folding plate. The patent in suit adopts the first device, the defendant's machine the second, and the crucial question before the court is this: Under all the circumstances of the case, is the second method, as compared with the first, within the doctrine of equivalents?"

The court, as we have seen, concluded, from the character of the Liddell patent, that "the second method," that is, the method of the Continental Company's machine, was "within the doctrine of equivalents."

Counsel, however, contends that the Circuit Court, in its decision, virtually gave Liddell a patent for a function by holding that he was entitled to every means to cause the forming plate to oscillate about its rear edge.

The distinction between a practically operative mechanism and its function is said to be difficult to define. Robinson on Patents, § 144, et seq. It becomes more difficult when a definition is attempted of a function of an element of a combination which are the means by which other elements are connected and by which they coäct and make complete and efficient the invention. But abstractions need not engage us. The claim is not for a function, but for mechanical means to bring into working relation the folding plate and the cylinder. This relation is the very essence of the invention, and marks the advance upon the prior art. It is the thing that never had been done before, and both the lower courts found that the machines of the Continental Company were infringements of it. It is not possible to say that the findings of those courts on that fact or on the fact of invention were clearly wrong, notwithstanding the great ability of the argument submitted against them.

2. The next contention of the petitioner is that a court of equity has no jurisdiction to restrain the "infringement of letters patent the invention covered by which has long and always and unreasonably been held in non-use instead of being made beneficial to the art to which it belongs." It will be observed that it is not urged that non-use merely of the patent takes jurisdiction from equity, but an unreasonable non-use. And counsel concedes indulgence to a non-use which is "non-chargeable to the owner of the patent," as lack of means, or lack of ability or opportunity to induce others to put the patent to use. In other words, a question is presented, not of the construction of the law simply but of the conduct of the patentee as contravening the supposed public policy of the law.

The foundation of the argument of the petitioner is, as we have intimated, the policy of the patent laws executing the purpose of the Constitution of the United States to promote the progress of science and useful arts by securing for limited times to inventors the exclusive right to their respective dis

coveries. Art. I, § 8. And it is urged that the non-use of an invention for seventeen years (of course, the whole term of the patent may be selected to test the argument) is not to promote the progress of the useful arts, and the contention is that equity should not give its aid to defeat the policy of the statute, but remit the derelict patentee to his legal remedy. The penalty does not seem to fit the case. It is conceded that the patent is not defeated; only that a particular remedy is taken away. It is conceded that the remedy at law remains. It is conceded, therefore, that a right has been conferred, but it is said that it may be infringed, though the policy of the law is violated. The petitioner, further to sustain its side of the question, refers to the provision in § 4921, giving power to the courts to grant injunctions. The provision is: "The several courts vested with jurisdiction of cases arising under the patent law shall have power to grant injunctions according to the course and principles of equity, to prevent the violation of any right secured by the patent, and the petitioner cites Root v. Railway Company, 105 U. S. 183, 216, for the contention that the statute does not confer power to grant the injunction, except as incidental to some other equity.

It may be well, however, before considering what remedies. a patentee is entitled to, to consider what rights are conferred upon him. The source of the rights is, of course, the law, and we are admonished at the outset that we must look for the policy of a statute, not in matters outside of it-not to circumstances of expediency and to supposed purposes not expressed by the words. The patent law is the execution of a policy having its first expression in the Constitution, and it may be supposed that all that was deemed necessary to accomplish and safeguard it must have been studied and provided for. It is worthy of note that all that has been deemed necessary for that purpose, through the experience of years, has been to provide for an exclusive right to inventors to make, use and vend their inventions. In other words, the language of complete monopoly has been employed, and though at first