tilities is vital to the maintenance of the Arm at its initial strength, and the manufacture is itself threatened if the enemy once obtain, aeronautically, the upper hand. Thus the life of an aeroplane in active service is a matter of only some three or four months, and the manufacturing resources of the country must thus be capable of replacing the whole active force of aeroplanes three or four times over in every year. On the other hand, our sources of supply, or those situated within raiding distance of hostile territory, would be seriously imperilled were the enemy to obtain, even for a short time, a sufficient preponderance of air power. The intention of thus making use of aeronautical ascendency to extinguish the enemy's sources of supply has been clearly manifested in the present war, as witness the raids executed against Friedrichshaven and other Zeppelin bases; the reason that such tactics have not been pushed to the extreme and followed to their logical conclusion is clearly that the raiding aeroplane, in respect of type, numerical strength, and organisation, is yet in its infancy.
For the above reason it is the author's opinion that the main aeronautical manufacturing resources of any country will eventually be established out of effective reach of hostile territory; in the case of Great Britain this indicates the selection of a position some three or four hundred miles from the continental littoral. The circumstances point ultimately to the industrial districts of Belfast and the Clyde, as appropriate centres for the production of both aeroplanes and so-called "seaplanes" in the quantities the future will demand. Such a position is out of range of existing hostile aircraft, and will probably remain so for many years to come. Looking beyond this it is a position giving such great possibilities of defence, that so long as we assume the motive power engine subject
197
