Argument for Respondent.

225 U.S.

Defendant does not contend that the Westinghouse improvement was of no value, but of very slight value: and does contend that the burden was upon complainant in the accounting to show that value in dollars and cents. To justify an award to complainant it must appear that defendant realized a profit from using the invention of Claim 4 over and above what it would have realized by using that which was open to it and which it had a right to use. Calkins v. Bertand, 8 Fed. Rep. 755-760; Maier v. Brown, 17 Fed. Rep. 736; Reed v. Lawrence, 29 Fed. Rep. 915; Mowry v. Whitney, 14 Wall. 620; Littlefield v. Perry, 21 Wall. 205.

The general rule is that the burden of proof is on complainant to show profit due to a patented improvement. Garretson v. Clark, 111 U. S. 120; Tomkinson v. Willets Mfg. Co., 34 Fed. Rep. 536; Mosher v. Joyce, 51 Fed. Rep. 441; Robbins v. Illinois Watch Co., 81 Fed. Rep. 957; Wales v. Waterbury Mfg. Co., 101 Fed. Rep. 182; Brickill v. Mayor of N. Y., 112 Fed. Rep. 65; Lattimore v. Hardsogg Mfg. Co., 121 Fed. Rep. 986; Cary Mfg. Co. v. De Haven, 139 Fed. Rep. 262; Westinghouse Air Brake Co. v. N. Y. Air Brake Co., 140 Fed. Rep. 545; Force v. Sawyer-Boss Mfg. Co., 143 Fed. Rep. 894.

The defendant showed affirmatively no substantial difference between the infringing and non-infringing transformers and the complainant did not prove the value of the slight difference, though the burden of proof was upon complainant. Garretson v. Clark, 111 U. S. 120; Keystone Mfg. Co. v. Adams, 151 U. S. 145; Canda Bros. v. Mich &c., 81 C. C. A. 420-423.

Complainant offered no evidence to rebut or contradict defendant's evidence as to the value of things defendant was free to use.

From no point of view is defendant estopped to show the degree of utility of the improvement covered by Claim 4. Gibbs v. Hoefner, 19 Fed. Rep. 332; Lamb Knit

Goods Co. v. Lamb Glove & M. Co. (C. C. A.), 120 Fed. Rep. 272; International Tooth Crown Co. v. Hanks &c. (C. C. A.), 111 Fed. Rep. 920; Lee v. Pillsbury, 49 Fed. Rep. 750.

The decree in the Carbide Case was interlocutory and not final and the matters therein covered are not, therefore, res judicata. Perkins v. Fourniquet, 6 How. 206; Keystone Iron Co. v. Martin, 132 U. S. 91–94; McGourkey v. Toledo &c., 146 U. S. 536; Rumford Chemical Works v. Hecker, Fed. Cases, No. 12133; Harmon v. Struthers, 48 Fed. Rep. 260; Morss v. Knapp, 37 Fed. Rep. 351; Roemer v. Neumann, 26 Fed. Rep. 332; David Bradley Mfg. Co. v. Eagle Mfg. Co., 58 Fed. Rep. 721.

Estoppel must be certain to every intent. Russell v. Place, 94 U. S. 606.

It is doubtful if complainant can urge res judicata in this court. Defendant could not bring the Carbide Case to this court for review. If complainant brings the judgment in that case before this court and invokes it, it may be reviewed by this court.

The prior act shown by the record may be examined as an aid in the interpretation of Claim 4, despite all the judgments that have been rendered under the patent in suit by the courts below. Vance v. Campbell, 1 Black, 427; Brown v. Piper, 91 U. S. 37; Dunbar v. Meyers, 94 U. S. 187; Eachus v. Broomall, 115 U. S. 429.

Complainant does not here contend that defendant's modified device is within Claim 4, which is an admission of the limited character of the claim.

MR. JUSTICE LAMAR, after making the foregoing statement of the case, delivered the opinion of the court.

The statute makes the decision of the Circuit Court of Appeals final in patent cases, and the plaintiff's petition for the writ of certiorari herein was not granted for the

purpose of reëxamining the court's ruling that defendant's Type M Transformer was not an infringement of Claim 4 of the Westinghouse patent. The writ was issued in view of the holding that, though the Master found that the defendant had made a profit of $132,000 from the sale of infringing transformers, the plaintiff could yet only recover $1 because it failed to separate the profits made by its patent from those made by the defendant's addition.

1. The question as to who has the burden of proof, in cases like this, is one of great practical importance and constantly arises in patent cases. There has been much controversy on the subject and a conflict in the decisions. The authorities cited in the briefs of the two litigants, and others bearing on the subject, have been examined, but we shall not undertake to separately review them, for they disagree not so much as to the rule as to its application. It will be sufficient for the present purposes to say that

(a) Where the infringer has sold or used a patented article, the plaintiff is entitled to recover all of the profits.

(b) Where a patent, though using old elements, gives the entire value to the combination, the plaintiff is entitled to recover all the profits. Hurlbut v. Schillinger, 130 U. S. 456, 472.

(c) Where profits are made by the use of an article patented as an entirety, the infringer is liable for all the profits "unless he can show-and the burden is on him to show-that a portion of them is the result of some other thing used by him." Elizabeth v. Pavement Co., 97 U. S. 126.

(d) But there are many cases in which the plaintiff's patent is only a part of the machine and creates only a part of the profits. His invention may have been used in combination with valuable improvements made, or other patents appropriated by the infringer, and each may have

jointly, but unequally, contributed to the profits. In such case, if plaintiff's patent only created a part of the profits, he is only entitled to recover that part of the net gains. He must, therefore, "give evidence tending to separate or apportion the defendant's profits and the patentee's damages between the patented feature and the unpatented features, and such evidence must be reliable and tangible, and not conjectural or speculative; or he must show, by equally reliable and satisfactory evidence, that the profits and damages are to be calculated on the whole machine, for the reason that the entire value of the whole machine, as a marketable article, is properly and legally attributable to the patented feature." Garretson v. Clark, 111 U. S. 120.

The real controversy arises in applying this principle to those cases where it is impossible to separate the single profit into its component parts.

2. In considering the question presented by the record here, it is to be borne in mind that Congress has legislated (Rev. Stat., § 4921) with a view of affording the patentee ample redress against the infringer. It not only makes the latter liable for damages-sometimes three-fold damages--but for all profits derived from the use or sale of plaintiff's invention. The rule as to the burden of proof has, however, been so applied that this statutory right has been often nullified by those infringers who had ingenuity enough to smother the patent with improvements belonging to themselves or to third persons. In such cases the greater the wrong the greater the immunity; the greater the number of improvements the greater the difficulty of separating the profits. And if that difficulty could only be converted into an impossibility the defendant retained all of the gains, because the injured patentee could not separate what the guilty infringer had made impossible of separation.

Manifestly such consequences demonstrate that either

the rule or its application is wrong. The rule is sound, for it but announces the general proposition that the plaintiff must prove its case and carry the burden imposed by law upon every person seeking to recover money or property from another. But the principle must not be pressed so far as to override others equally important in the administration of justice. It may serve to illustrate the rule and its limitations, if, at the risk of stating the obvious, we apply it to the various steps of this case.

The plaintiff proved its patent and that it had been infringed by the defendant in the manufacture of several thousand transformers which sold for $955,000. The patent was itself evidence of the utility of Claim 4, and the defendant was estopped from denying that it was of value. Lehnbeuter v. Holthaus, 105 U. S. 94. But no matter how great its presumptive or actual value it did not follow that the defendant had made a profit by the sale of the infringing transformers. And so, having sued for profits, the Westinghouse Company was under the burden of showing they had been made. This it did to the satisfaction of the Master, who found that the defendant had netted $132,000 from their sale.

The defendant then had the right either to disprove the plaintiff's case or to offer evidence in mitigation, or both. Accordingly it submitted evidence tending to show that the spaces added by the defendants were noninfringing and valuable improvements which had contributed to the making of the profits. In reply the Westinghouse Company insisted that Claim 4 was an entirety, covering a circulatory system in and around a transformer placed in an oil-filled receptacle; that it embraced the "intervening spaces in the coil" because at least a part of the coil was in the core; that if these spaces were held not to be infringements they had in fact, as employed by the defendant, added nothing to the profits, but on the contrary had crippled the coil and lessened the electrical