339 U.S.

Opinion of the Court.

persuasiveness and weight of evidence. It is to be decided by the trial court and that court's decision, under general principles of appellate review, should not be disturbed unless clearly erroneous. Particularly is this so in a field where so much depends upon familiarity with specific scientific problems and principles not usually contained in the general storehouse of knowledge and experience.

In the case before us, we have two electric welding compositions or fluxes: the patented composition, Unionmelt Grade 20, and the accused composition, Lincolnweld 660. The patent under which Unionmelt is made claims essentially a combination of alkaline earth metal silicate and calcium fluoride; Unionmelt actually contains, however, silicates of calcium and magnesium, two alkaline earth metal silicates. Lincolnweld's composition is similar to Unionmelt's, except that it substitutes silicates of calcium and manganese-the latter not an alkaline earth metal-for silicates of calcium and magnesium. In all other respects, the two compositions are alike. The mechanical methods in which these compositions are employed are similar. They are identical in operation and produce the same kind and quality of weld.

The question which thus emerges is whether the substitution of the manganese which is not an alkaline earth metal for the magnesium which is, under the circumstances of this case, and in view of the technology and the prior art, is a change of such substance as to make the doctrine of equivalents inapplicable; or conversely, whether under the circumstances the change was so insubstantial that the trial court's invocation of the doctrine of equivalents was justified.

Without attempting to be all-inclusive, we note the following evidence in the record: Chemists familiar with the two fluxes testified that manganese and magnesium were similar in many of their reactions (R. 287, 669). There is testimony by a metallurgist that alkaline earth

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Opinion of the Court.

metals are often found in manganese ores in their natural state and that they serve the same purpose in the fluxes (R. 831-832); and a chemist testified that "in the sense of the patent" manganese could be included as an alkaline earth metal (R. 297). Much of this testimony was corroborated by reference to recognized texts on inorganic chemistry (R. 332). Particularly important, in addition, were the disclosures of the prior art, also contained in the record. The Miller patent, No. 1,754,566, which preceded the patent in suit, taught the use of manganese silicate in welding fluxes (R. 969, 971). Manganese was similarly disclosed in the Armor patent, No. 1,467,825, which also described a welding composition (R. 1346). And the record contains no evidence of any kind to show that Lincolnweld was developed as the result of independent research or experiments.

It is not for this Court to even essay an independent evaluation of this evidence. This is the function of the trial court. And, as we have heretofore observed, "To no type of case is this . . . more appropriately applicable than to the one before us, where the evidence is largely the testimony of experts as to which a trial court may be enlightened by scientific demonstrations. This trial occupied some three weeks, during which, as the record shows, the trial judge visited laboratories with counsel and experts to observe actual demonstrations of welding as taught by the patent and of the welding accused of infringing it, and of various stages of the prior art. He viewed motion pictures of various welding operations and tests and heard many experts and other witnesses." 336 U. S. 271, 274–275.

The trial judge found on the evidence before him that the Lincolnweld flux and the composition of the patent in suit are substantially identical in operation and in result. He found also that Lincolnweld is in all respects equivalent to Unionmelt for welding purposes. And he concluded that "for all practical purposes, manganese silicate

can be efficiently and effectually substituted for calcium and magnesium silicates as the major constituent of the welding composition." These conclusions are adequately supported by the record; certainly they are not clearly erroneous.2

It is difficult to conceive of a case more appropriate for application of the doctrine of equivalents. The disclosures of the prior art made clear that manganese silicate was a useful ingredient in welding compositions. Specialists familiar with the problems of welding compositions understood that manganese was equivalent to and could be substituted for magnesium in the composition of the patented flux and their observations were confirmed by the literature of chemistry. Without some explanation or indication that Lincolnweld was developed by independent research, the trial court could properly infer that the accused flux is the result of imitation rather than experimentation or invention. Though infringement was not literal, the changes which avoid literal infringement are colorable only. We conclude that the trial court's judgment of infringement respecting the four flux claims was proper, and we adhere to our prior decision on this aspect of the case.

Affirmed.

MR. JUSTICE MINTON took no part in the consideration or decision of this case.

MR. JUSTICE BLACK, with whom MR. JUSTICE DOUGLAS concurs, dissenting.

I heartily agree with the Court that "fraud" is bad, "piracy" is evil, and "stealing" is reprehensible. But in

2 Rule 52 (a), Federal Rules of Civil Procedure, provides in part: "Findings of fact shall not be set aside unless clearly erroneous, and due regard shall be given to the opportunity of the trial court to judge of the credibility of the witnesses."

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this case, where petitioners are not charged with any such malevolence, these lofty principles do not justify the Court's sterilization of Acts of Congress and prior decisions, none of which are even mentioned in today's opinion.

The only patent claims involved here describe respondent's product as a flux "containing a major proportion of alkaline earth metal silicate." The trial court found that petitioners used a flux "composed principally of manganese silicate." Finding also that "manganese is not an alkaline earth metal," the trial court admitted that petitioners' flux did not "literally infringe" respondent's patent. Nevertheless it invoked the judicial "doctrine of equivalents" to broaden the claim for "alkaline earth metals" so as to embrace "manganese." On the ground that "the fact that manganese is a proper substitute .. is fully disclosed in the specification" of respondent's patent, it concluded that "no determination need be made whether it is a known chemical fact outside the teachings of the patent that manganese is an equivalent . Since today's affirmance unquestioningly follows the findings of the trial court, this Court necessarily relies on what the specifications revealed. In so doing, it violates a direct mandate of Congress without even discussing that mandate.

R. S. § 4888, as amended, 35 U. S. C. § 33, provides that an applicant "shall particularly point out and distinctly claim the part, improvement, or combination which he claims as his invention or discovery." We have held in this very case that this statute precludes invoking the specifications to alter a claim free from ambiguous language, since "it is the claim which measures the grant

1 For this reason the tidbits of evidence painstakingly selected from the record by this Court have no significance, since the trial court avowedly did not look beyond the specifications themselves.

BLACK, J., dissenting.

339 U.S.

to the patentee." 2 Graver Mfg. Co. v. Linde Co., 336 U. S. 271, 277. What is not specifically claimed is dedicated to the public. See, e. g., Miller v. Brass Co., 104 U. S. 350, 352. For the function of claims under R. S. § 4888, as we have frequently reiterated, is to exclude from the patent monopoly field all that is not specifically claimed, whatever may appear in the specifications. See, e. g., Marconi Wireless Co. v. United States, 320 U. S. 1, 23, and cases there cited. Today the Court tacitly rejects those cases. It departs from the underlying principle which, as the Court pointed out in White v. Dunbar, 119 U. S. 47, 51, forbids treating a patent claim “like a nose of wax which may be turned and twisted in any direction, by merely referring to the specification, so as to make it include something more than, or something different from, what its words express. The claim

is a statutory requirement, prescribed for the very purpose of making the patentee define precisely what his invention is; and it is unjust to the public, as well as an evasion of the law, to construe it in a manner different from the plain import of its terms." Giving this patentee the benefit of a grant that it did not precisely claim is no less "unjust to the public" and no less an evasion of R. S. § 4888 merely because done in the name of the "doctrine of equivalents."

In seeking to justify its emasculation of R. S. § 4888 by parading potential hardships which literal enforcement might conceivably impose on patentees who had for some reason failed to claim complete protection for their discoveries, the Court fails even to mention the program for alleviation of such hardships which Congress itself

2 This Court's approval of the trial judge's resort to specifications is ironic as well as unfortunate. In its original opinion this Court rejected respondent's contention that the very language invoked here to support infringement should be applied to validate a claim otherwise too broad to be upheld. 336 U. S. 271, 277.