"The powers . . . granted by [the commerce clause] are not confined to the instrumentalities of commerce, or the postal service known or in use when the Constitution was adopted, but they keep pace with the progress of the country, and adapt themselves to the new developments of time and circumstances. They extend from the horse with its rider to the stage-coach, from the sailing vessel to the steamboat, from the coach and the steamboat to the railroad, and from the railroad to the telegraph, as the new agencies are successively brought into use to meet the demands of increasing population and wealth." 7

The doctrine thus laid down in the Pensacola case has never

5 Railway Co. v. Husen, 95 U. S. 465; 24 L. ed. 527.

6 Pensacola Tel. Co. v. W. U. Tel. Co., 96 U. S. I; 24 L. ed. 703; W. U. Tel. Co. v. Texas, 105 U. S. 460; 26 L. ed. 1067; Leloup v. Mobile. 127 U. S. 640; 8 Sup. Ct. Rep. 1383; 32 L. ed. 31; W. U. Tel. Co. v. Mass., 125 V. S. 530; 8 Sup. Ct. Rep. 961; 31 L. ed. 790.

The communications passing between a Correspondence School and its pupils are interstate commerce. International Text Book Co. v. Pigg, 217 been questioned. Telephonic messages are, of course, covered by it. No case involving the transmission of wireless messages has. arisen, but without doubt they would be treated as commerce, and the same would be true of messages and persons carried by balloons and other apparatus for the navigation of the air.

U. S. 9l ; 30 Sup. Ct. Rep. 481.

7 Pensacola Tel. Co. v. W. U. Tel. Co., 96 U. S. 1; 24 L. ed. 708.