A certain amount of reliance could also be placed on civil machines temporarily borrowed for purely policing measures in uncivilized countries, or for the assistance of Government during civil disturbances; and for such purposes it should not be difficult to devise a scheme, especially when the State exercises a measure of control through the grant of subsidies, for the obligatory enrolment of civil commercial pilots in the reserve, and for periodical refresher courses for pilots, who are not actually in the service of companies, at civil aerodromes. Such systems are in force in France and Canada. In the event of war the independent striking air force could thus count upon a large proportion of civil reserve pilots and machines. Air, allied to chemistry and the submarine, will be a difficult combination to withstand. The more its potential terrors are grasped, the less likely is war to be loosed upon the world, and it cannot be realized too clearly how much more easily than any other instrument of warfare aircraft and gas can be cheaply and secretly prepared by a would-be belligerent. Meanwhile, if civil aviation can be built up as a productive organization to a position relative to that held by our mercantile marine, we must understand that it will ensure air supremacy better than a large unproductive outlay on armaments. And I am convinced that, with public support, this can, and will, be done. Others will do it if we do not. But air power, although drawing its vitality from the expansion of air commerce and the growth of the civil aircraft industry, must at the same time rely upon the nucleus of a highly trained and technical air force. Service aviation must be the spearhead, civil aviation the shaft, of our air effort.