Explosives. Proposed regulations, supplement to Regulations for transportation of explosives and other dangerous articles in freight, express, and baggage services, and by water on freight and passenger vessels as indicated (see par. 2), including specifications for shipping containers, prescribed under act of Mar. 4, 1921, binding upon all common carriers engaged in interstate or foreign commerce by rail and water within limits of jurisdiction of United States, and upon all shippers making shipments via such carriers.