(a) First Division. The First Division will have jurisdiction over disputes involving train-and yard-service employees of carriers; that is, engineers, firemen, hostlers, and outside hostler helpers, conductors, trainmen, and yard-service employees.

(b) Second Division. The Second Division will have jurisdiction over disputes involving machinists, boilermakers, blacksmiths, sheet-metal workers, electrical workers, car men, the helpers and apprentices of all the foregoing, coach cleaners, power-house employees, and railroad-shop laborers.

(c) Third Division. The Third Division will have jurisdiction over disputes involving station tower, and telegraph employees, train dispatchers, maintenance-of-way men, clerical employees, freight handlers, express, station, and store employees, signal men, sleeping-car conductors, sleeping-car porters, and maids and dining-car employees.

(d) Fourth Division. The Fourth Division will have jurisdiction over disputes involving employees of carriers directly or indirectly engaged in transportation of passengers or property by water, and all other employees of carriers over which jurisdiction is not given to the First, Second, and Third Divisions.