A company contracted with W. to allow him “to collect clean and take away all mundic sand and pyrites from the company’s battery after the mundic sand and pyrites had passed from the tables and amalgamating barrels and outside the company’s battery house” at so much per ton. They had not then, and did not erect, any amalgamating barrels, but used blanket tables; and, some time after the agreement, instead of allowing the sand to pass from the tables outside the battery-house, saved the sand from them, and extracted the gold from it, allowing none of the sand to go to the plaintiff.