A satisfactory division of powers. The problem which all federal states have to solve is how to secure an efficient Central Government, while allowing scope for the diversities, and free play to the authorities, of the units. It is, to adopt Bryce ‘s metaphor, to keep the centrifugal and centripetal forces in equilibrium, so that neither the planet states shall fly off into space, nor the sun of the Central Government draw them into its consuming fires. The general principle on which the division of powers should rest is fairly obvious. ‘Whatever concerns the nation as a whole should be placed under the control of the national Government. All the matters which are not primarily of common interest should remain in the hands of the several states. Such subjects as foreign affairs, maritime shipping and currency, are clearly of common interest and are everywhere federal ; municipal institutions, hospitals, local public works, property and civil rights, and the administration of justice within, the state, are clearly of the local nature and are everywhere allotted to the units. On a number of subjects, the common interests, or the purely local interest, is not quite so clear, and, therefore, the details of the division vary under different federal conditions.