678 PEDEBAL EEPOETEB. �Samb — Statb of THE ART. — In such case the state of the art when tho invention was made is always to be considered. �Same — Peofits incapable of Mbasueement. — Alfhotigh an infringer may be answerable in damages, he is not to be Iield liable for profits, unless there is some satisfactory evidence from which the value of the advantage derived from the use of the invention can be measured. �Same — Combinatioiî op Locomotivb with Sv^ing-Teuck.— The use of a combination of a swing- truck with a locomotive having flanges on ail its driving-wheels, not shown to have any advantage over the use of a locomotive with plain forvvard driving-wheels and a rigid truck. �Damages — Standard of — Royalties. — Where a patentee had afixed roy- alty for the use of his patent, Tidd, that this was a proper standard by which to measure his damages from an infringement. �Same — Inteeest on Royalties. — In such case, in estimating the dam- ages, interest should be added to the royalties from the time of infringe- ment to the date of the decree. �Exceptions to the report of a master appointed to state an account of the profits realized by defendants by reason qf an infringement of complainants' patent, and also to aasess the damages caused by such infringement. �The master (Kobert N. Willson, Esq.) reported that com- plainants' patent was for a combination of a swiùg-truck with a locomotive; that the evidence showed that prier to using such invention defendants had used locomotives having a rigid truck and flanged driving-wheels ; that the advantages derived from the use of complainants' invention could have been obtained by the use of a locomotive having a rigid truck and having no flanges on its forward driving-wheels, and that this latter form of locomotive was then in common and un- restricted use. He also reported that in estimating profits the comparison of advantages should be made between com- plainants' invention and an engine having a rigid truck and forward driving-wheels without flanges; that complainants had scarcely attempted to meet such a comparison, but relied, apparently, upon a comparison with a locomotive having ail its driving-wheels flanged, and that upon the evidence he was unable to find that defendants had realized any profits. He also i-eported that complainants had a fixed royalty of $100 per engine for the use of their invention, and adopting this as a measure of damages, and adding interest, he assessed the damages at $89,644. Both parties filed exceptions. ����
