Charles Evans Hughes, Ohio Oil Company v. Conway (281 U.S. 146…
“ Gravity is said to be an index of relative value of oils only in the same pool or district, and oils of different gravity are produced in the same fields and from the same tracks of land and sometimes from the same sand. But it appears that, with respect to paraffine base oils, the higher the gravity, the greater is the gasoline content which as between these oils is largely determinative of price. Gravity in such cases is a rough and familiar method of approximating the gasoline content, and in many fields price quotations of crude oil above 28 degrees are graduated according to gravity. ”
