A custom among commission merchants and brokers (not unlike the clearing-house system) by which they exchange contracts for sale against contracts for purchase, or reciprocally cancel such contracts. adjust differences of price between themselves, and surrender margins. See Ward v. Vosburgh (C. C.) 31 Fed. 12; Williar v. Irwin, 30 Fed. Cas. 38; Pnrdl’idge v. Cutler, OS 111. App. 573; Samuels v. Oliver, 130 111. 73, 22 N. E. 499.