(dissenting).
The curing of tobacco by heating and drying the air in the barn in which it is hung is as old as the industry itself; and the essential elements of the procedure have been known and used for a long time. They comprise the admission of air through openings in the walls of the barn near the floor and heating the air so that it will rise through the hanging tobacco suspended in the barn and pass out through a ventilator in the roof. Originally wood, and later coal, was burned in an outside furnace which imparted heat to pipes or flues placed inside the building below the tobacco whereby the inside air was heated to the proper temperature. When this method became too expensive by reason of the cost of fuel and the cost of tending the furnace, open flame oil burners placed inside the barn under a hood or casing were substituted.
The patentee in the pending case contributed none of these steps in the development of the art. The validity of the patent in suit depends on one thing only, that is, an air intake pipe let through the side walls of the barn to receive fresh air and conduct it to the space above the oil burners and beneath the hood. Even this device was not new in its entirety. The Smith Patent, No. 2,051,348, for example, showed an air intake pipe which discharged air in the vicinity of the burners but not directly into the space underneath the hood above the burners, although some of the air admittedly entered this space. The question for decision is whether this contribution amounted to invention. Devices equally this simple and obvious after the event have been accorded this rank. A classic example is Eibel Process Co. v. Paper Co., 261 U.S. 45, 43 S.Ct. 322, 67 L.Ed. 523, where the mere elevation in the pitch of an element in a machine was held to involve invention because it solved a problem that had vexed the industry and thereby turned failure into success.
Unfortunately for the patentee herein, there is no finding that the discharge of the air under the hood solved any problem or made any substantial improvement to the process of curing tobacco. The finding of the District Judge who saw the witnesses was quite to the contrary. He said : “There was some conflict in the testimony given with respect to any improvement in the quality when curing with oil stoves and using outside air directly heated in the oil stove, as compared with previous practices of curing, using coal or wood as the fuel, or using a heated flue. Certain of the witnesses testified that the use of oil stoves and the outside air directly heated thereby, gave more weight to the tobacco and thus increased the price which it brought at the warehouse. This testimony was not convincing. It was not based on any tests, experiments or observations of a character which would be necessary to prove that the practice of using oil burners and directly heated outside air gave added weight or better quality to the tobacco. Tobacco growers of experience testified that the use of oil stoves in the manner referred to did not result in any improvement in the qual*786ity of the tobacco, and did not cause it to bring a better price. In fact, it appears that there is no substantial variation in the resulting cured tobacco, no matter which of the methods or practices referred to is used. The weight of the evidence is that the method of curing tobacco, using oil stoves and outside air heated over the flame and beneath the hood, brought no improvement in quality or price of the tobacco. The advantages of cheapness and convenience which were present in the use of oil stoves, are only those which might normally be expected.” (Italics supplied.)
This finding is binding upon us. Federal Rule of Civil Procedure 52(a), 28 U.S. C.A. following section 723c, declares that “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.” None of us is able to say that this finding of the District Judge was clearly erroneous, as will appear from the discussion in the foregoing opinion of this court. The conclusion seems to be inevitable that the Florence-Mayo system of curing tobacco, effective and successful though it seems to be, does not involve the element of invention.
The question of patentability always involves the exercise of an informed judgment, and opinions may easily differ. There is, however, one feature of this case, fatal to the patent, which hardly seems to admit of a difference of opinion. It is the fact that the patentee in the course of the proceedings upon his original application for the patent abandoned a claim which included the one feature of the process above described upon which the validity of the patent depends. The claim in question was rejected by the Patent Office and ■the patentee acquiesced in its rejection and did not appeal. The law in such a situation was declared by the Supreme Court in Altoona Publix Theatres, Inc. v. American Tri-Ergon Corp., 294 U.S. 477, 492, 55 S. Ct. 455, 461, 79 L.Ed. 1005, where it was said that “it has long been settled that a claim abandoned or rejected in the Patent Office with the acquiescence of the applicant cannot be revived in a reissued patent” ; and in accordance with the rule it is held that one who acquiesces in a rejection of a claim, well knowing the significance of his act, is deemed to have abandoned the claim. Mahn v. Harwood, 112 U.S. 354, 359, 5 S.Ct. 174, 6 S.Ct. 451, 28 L.Ed. 665; Union Switch & Signal Co. v. Louisville Frog, Switch & Signal Co., 6 Cir., 73 F.2d 550, 552.
Claim 4 of the original patent which was abandoned in the Patent Office,' and Claim 2 of the reissue patent, set out in the foregoing opinion of the court, cover the same ground, involve the same elements and are of equal breadth. Each of them calls'for a tobacco curing building, a ventilating opening in the roof, supports for the tobacco in the structure and open flame oil burners with overlying hood. Each claim also described the feature on which the issue of invention depends. In claim 4 this element is described as “manually controlled air intake means connected to each hood and receiving air from the exterior of the building structure”; while claim 2 describes it in the following words: “An air intake opening into the space above the heating means and extending through a side wall of the barn to receive fresh air.” Obviously these two descriptions are substantially the same, and if any lingering doubt on the point remains, it is resolved by the identical drawings which accompanied both the original and the reissue application which showed a pipe running from the exterior of the building through the wall and discharging the air into the space beneath the hood.
Claim 2 of the reissue also explains the reason why the outside air is conducted to the hood. The explanation is contained in the clause, “whereby fresh air from the outside will be mixed in said hood with the heated gases from the burner and will thereby be conditioned - before passing up- ■ wardly into the barn.” This clause does not appear in claim 4 of the original application. It is obvious, however, that the clause is immaterial to the issue of patentability and adds nothing thereto; for it is well settled, as will appear from decision of this court in DeStubner v. United Carbon Co., 4 Cir., 163 F.2d 735, 743, and the cases *787cited therein, that, on the one hand, it is not necessary that a patentee understand the scientific basis for his invention and on the other hand, an explanation of the law controlling the operative steps of a process does not constitute invention.
The rule of patent law under discussion has a sound basis in that the abandonment of a claim or the failure of a patentee to cover an element of a device by a claim justifies the assumption that the matter disclosed but not claimed in the patent is within the public domain. In the instant case, the infringing device was put on the market before the grant of the reissue although after the application therefor had been filed.
I think the judgment of the District Court should be affirmed. It takes something more than the commercial success of a device and the imitation of one’s product by a competitor to establish the validity of a patent