By act of 1007, entitled "An Act to Promote the Safety of Employees and Travellers upon Railroads by Limiting the Hours of Service of Employees Thereon" Congress has undertaken to determine the number of hours a day which employees upon interate railways may be permitted or required to labor. This measure relates to the contract between the employing companies and their employees and thus falls in the same category as the Employers' Liability Act. Its relation to safe and efficient service would, however, seem to be somewhat more direct than the latter act.

15 "Commerce, in its simplest signification, means an exchange of goods; but, in the advancement of .society, labor, transportation, intelligence,care.and various mediums of exchange, become commodities and enter into commerce; the subject, the vehicle, the agent, and their various operations become the objects of commercial regulation." Justice Johnson in Gibbons v. Ogden, 9 Wh. 1; 6 L. ed. 23.

"It is true that the commercial power conferred by the Constitution is one without limitation. It authorizes legislation with respect to all the subjects of foreign and interstate commerce, the persons engaged in it, and the instniments by which it is carried on." Sherlock v. Ailing, 03 U. S. 99; 23 L. ed. 819.

"The power . . . embraces within its control all instrumentalities by which that commerce may be carried on, and the means by which it may be aided and encouraged." Gloucester Ferry Co. v. Pa.. 114 U. S. 196; 5 Sup. Ct. Rep. 826; 29 L. ed. 158. The Safety Appliance Acts also meet the test suggested by Cooke.

16 196 U. S. 1. 25 Sup. Ct. Rep. 158; 49 L. ed. 363.

17 157 Fed. Rep. 321.