BMIGH V, B. & 0. E. 00. 289 �rately the money value of the advantages which the defend- ant lias derived from its use of the patent is undoubtedly diffi- cult. The complainants have been obliged in great measure to procure their witnesses from railroads whose interests are with the defendant, and the Stevens brake, as used on other roads, has been a modified and in many instances an unskil- fuUy made fonn of the patented device. �Considering ail the difficulties and embarrasments of the complainants' position, we are satisfied, after a careful exam- ination of the evidence, that they have substantially sustained the burden of proof which the law imposes upon them, and that the master's findings are warranted by the testimony. It is to be considered, however, that this is a patent which was only valuable to the patentee as he could induce railroads to use it and pay him for its use and that it was worth nothing to him as a monopoly. �An established license fee, when one is proved, is unques- tionably the safest rule of compensation in sueh cases, and in view of the great difficulty of proving with exactness the profits which have accrued to the defendant, the license fee found by the master to have existed, at least during the latter portion of the life of the patent, commends itself to us, under the circumstances of this case, as the measure of compensa- tion least likely to do injustice to either party. �It was said by the supreme court in Packet Co. v. Sickles, 19 Wall. 618, that taking profits as the basis of compensa- tion in. courts of equity had produced resulta creating distrust of its faimess. And in Burdell v. Denig, 92 U. S. 720, that court, after recognizing that profits are the primary rule in equity, and a license fee in actions at law, say :• "No doubt, in the absence of satisfactory evidence of either class in the forums to which it is most appropriate, the other may be resorted to as one of the elements on which the damages or the compensation may be ascertained." �The testimony shows that after the validity of this patent was sustained by Judge Drummond in the United States cir- cuit court for the northern district of Illinois, and after the decree of that court in 1866 affirming the master's report in �v.6,no.3— 19 ��� �
