covers. Opinion of the Court. If at one time he insists on too much, and at another on too little, he does not thereby work any prejudice to the rights actually secured to him.” Other cases to the same effect are Merrill v. Yeomans, 94 U. S. 568; Burns v. Meyer, 100 U. S. 671; and Sutter v. Robinson, 119 U. S. 530. It is true that, in a case of doubt, where the claim is fairly susceptible of two constructions, that one will be adopted which will preserve to the patentee his actual invention; but if the language of the specification and claim shows clearly what he desired to secure as a monopoly, nothing can be held to be an infringement which does not fall within the terms the patentee has himself chosen to express his invention. The principle announced by this court in Vance v. Campbell, 1 Black, 427, that, where a patentee declares upon a combination of elements which he asserts constitute the novelty of his invention, he cannot in his proofs abandon a part of such combination and maintain his claim to the rest, is applicable to a case of this kind where a patentee has claimed more than is necessary to the successful working of his device. Applying these familiar principles to the case under consideration, we are forced to the conclusion that the curved hook of the defendant is not an infringement of the double spring described in the plaintiff's specification and claim. While a single spring or hook embracing the fore wale of a collar may be equally as efficacious, the patentee is no more at liberty to say that the spring encircling the after wale is immaterial and. useless than was the patentee in Vance v. Campbell to discard one of the elements of his combination upon the same ground. This was evidently the theory of the patentee himself, since, a little more than two months after this patent was issued, in a letter to the Patent Office of September 2, 1882, in which he made application for his second patent, covering the singleroll spring, he stated that "the single-roll spring must be conceded to be a structure positively and unequivocally different from the two-roll spring." There being no infringement of this patent, there can be no recovery upon it. (2) The second patent was principally contested upon the ground of want of invention. In his specification the patentee Opinion of the Court. states it to be an improvement upon his prior patent, but dif féring materially from it in the fact that "this spring has but one curved portion, intended for the fore roll only of the collar, instead of a curved portion for the fore roll and one for the back roll." It seems from his letter to the Patent Office of September 2, 1882, to which reference has already been made, that in endeavoring to practice the invention in his prior patent, he found that the two-roll spring was not generally applicable to collars of different sizes, as it had been supposed it would be; as the rolls in collars of different sizes and of different make varied so much that, while it would make a pad applicable to collars of different sizes for light work, the same pad could not be used on collars for heavy work, and hence the invention proved to be imperfect. This resulted in the invention of the single-roll spring of his second application. Practically, the only novelty consists in cutting the doubleroll spring in two and using the fore roll only. While this enables the pad to be located on the collar more readily than when two springs were used, the roll performs the same function as in the prior patent, and the patent can only be sustained upon the theory that the discarding of the after roll involved invention. What shall be construed as invention within the meaning of the patent laws has been made the subject of a great amount of discussion in the authorities, and a large number of cases, particularly in the more recent volumes of reports, turn solely upon the question of novelty. By some, invention is described as the contriving or constructing of that which had not before existed; and by another, giving a construction to the patent law, as "the finding out, contriv ing, devising or creating something new and useful, which did not exist before, by an operation of the intellect." To say that the act of invention is the production of something new and useful does not solve the difficulty of giving an accurate definition, since the question of what is new as distinguished from that which is a colorable variation of what is old, is usually the very question in issue. To say that it involves an operation of the intellect, is a product of intuition, Opinion of the Court. or of something akin to genius, as distinguished from mere mechanical skill, draws one somewhat nearer to an appreciation of the true distinction, but it does not adequately express the idea. The truth is the word cannot be defined in such manner as to afford any substantial aid in determining whether a particular device involves an exercise of the inventive faculty or not. In a given case we may be able to say that there is present invention of a very high order. In another we can see that there is lacking that impalpable something which distinguishes invention from simple mechanical skill. Courts, adopting fixed principles as a guide, have by a process of exclusion determined that certain variations in old devices do or do not involve invention; but whether the variation relied upon in a particular case is anything more than ordinary mechanical skill is a question which cannot be answered by applying the test of any general definition. Counsel for the plaintiff in the case under consideration has argued most earnestly that the only practical test of invention is the effect of the device upon the useful arts-in other words, that utility is the sole test of invention, and, inferentially at least, that the utility of a device is conclusively proven by the extent to which it has gone into general use. He cited in this connection certain English cases which go far to support his contention. These cases, however, must not be construed in such way as to control the language of our statute, which limits the benefits of patent laws to things which are new as well as useful. By the common law of England, an importer-the person who introduced into the kingdom from any foreign country any useful manufacture was as much entitled to a monopoly as if he had invented it. Thus in Darcy v. Allin, Noy, 173, it is stated that "where any man, by his own charge and industry, or by his own wit or invention, doth bring any new trade into the realm, or any engine tending to the furtherance of a trade that never was used before the king may grant to him a monopoly patent . . of the good that he doth bring by his invention to the commonwealth," citing several instances of skill imported from foreign countries. In Edgebury v. Stephens, 1 Webster's Pat. Cas. 35, in consideration Opinion of the Court. it was said: "The act [of monopolies] intended to encourage new devices useful to the kingdom, and whether learned by travel or by study it is the same thing." It is evident that these principles have no application to the patent system of the United States, whose beneficence is strictly limited to the invention of what is new and useful, and that the English cases construing even their more recent acts, must be received with some qualification. That the extent to which a patented device has gone into use is an unsafe criterion even of its actual utility, is evident from the fact that the general introduction of manufactured articles is as often effected by extensive and judicious advertising, activity in putting the goods upon the market and large commissions to dealers, as by the intrinsic merit of the articles themselves. The popularity of a proprietary medicine, for instance, would be an unsafe criterion. of its real value, since it is a notorious fact that the extent to which such preparations are sold is very largely dependent upon the liberality with which they are advertised, and the attractive manner in which they are put up and exposed to the eye of the purchaser. If the generality of sales were made the test of patentability, it would result that a person by securing a patent upon some trifling variation from previously known methods might, by energy in pushing sales or by superiority in finishing or decorating his goods, drive competitors out of the market and secure a practical monopoly, without in fact having made the slightest contribution of value to the useful arts. The very case under consideration is not barren of testimony that the great success of the McClain pads and clasping hooks, a large demand for which seems to have arisen and increased year by year, is due, partly at least, to the fact that he was the only one who made the manufacture of sweat pads a specialty, that he made them of a superior quality, advertised them in the most extensive and attractive manner, and adopted means of pushing them upon the market, and thereby largely increased the extent of their sales. Indeed it is impossible from this testimony to say how far the large sales of these pads is due to their superiority to others, or to the energy with which they were forced upon the market. While this court has held in a number of cases, even so late as Magowan v. The New York Belting and Packing Co. ante, 332, decided at the present term, that in a doubtful case the fact that a patented article had gone into general use is evidence of its utility, it is not conclusive even of that much less of its patentable novelty. In no view that we have been able to take of the case can we sustain the second McClain patent. We do not care to inquire how far it was anticipated by the various devices put in evidence, showing the use of a similar spring for analogous purposes, since we are satisfied that a mere severance of the double spring does not involve invention, at least in the absence of conclusive evidence that the single spring performs some new and important function not performed by it in the prior patent. The evidence upon this point is far from satisfactory, and the decree of the Circuit Court must, therefore, be Affirmed. The CHIEF JUSTICE and MR. JUSTICE GRAY did not hear the argument and took no part in the decision of this case. McLEAN v. CLAPP. APPEAL FROM THE CIRCUIT COURT OF THE UNITED STATES FOR THE NORTHERN DISTRICT OF ILLINOIS. No. 31. Argued October 15, 16, 1891.- Decided November 2, 1891. Grymes v. Sanders, 93 U. S. 55, affirmed and applied to the point that where a party desires to rescind a contract upon the ground of mistake or fraud, he must, upon discovery of the facts, at once announce his purpose and adhere to it, and that if he be silent, and continue to treat the property as his own, he will be held to have waived the objection, and will be conclusively bound by the contract, as if the mistake or fraud had not occurred. A holder of the legal title to real estate who has no equitable interest therein, cannot, by his act done without the knowledge or consent of the holder of the equitable title, who is in possession of and residing on the premises claiming title, rescind a completed settlement of a mortgage |