Section 29 of the Act declares: 'That no person shall mix for sale naphtha and illuminating oils, or shall knowingly sell or keep for sale, or offer for sale such mixture, or shall sell or offer for sale oil made from petroleum for illuminating purposes, inflammable at less temperature or fire-test than 110 degrees Fahrenheit; and any person so doing, shall be held to be guilty of a misdemeanor, and on conviction thereof by indictment or presentment in any court of the United States having competent jurisdiction, shall be punished by fine, &c., and imprisonment,' &c. Dewitt (D) was indicted, for offering for sale, at Detroit, in Michigan, oil made of petroleum of the description specified. There was no allegation that the sale was in violation or evasion of any tax imposed on the property sold. It was alleged only that the sale was made contrary to law. The Circuit Court certified two questions to the court: (1) whether the facts charged in the indictment constituted an offense, and (2) whether §29 of the Act was a valid and constitutional law of the United States.