Cookingham

(after stating the facts as above). Our understanding of Warren’s invention is that the mineral aggregate detailed by him of itself resists displacement by traffic. Stability is obtained by following his idea, and is due to the arrangement of the mineral • structure which enables the use of a softer asphalt than would be otherwise practical, and'this is so by reason of the fact that a greater proportion of the wear and strain is carried by the mineral elements than by the binding constituent.

An unusually long history of litigation surrounds the Warren patent. In Warren Bros. Co. v. Owosso (1909) 166 F. 309 , 92 C. C. A. 227 , the Court of Appeals for the Sixth Circuit construed the Warren patent, and through ' Judge Lurton said: “Warren’s invention, shortly stated, consists in the discovery that an aggregate of large and small pieces of stone, together with a certain proportion of stone dust, all mixed together and thoroughly permeated with bitumen or asphalt, results, when set, in a compact, stable structure, and is less liable to disintegrate from traffic or weather than- any other method of grading or arranging the mineral constituents. Under the evidence, the particles are…