In this book the author has sketched swiftly the slow stages by which in each of these fields of activity success has beenby beenattained. He has collated from the immense mass of records ofattained. Of the activities of both submarines and aircraft enough interestingthe interesting data to show the degree of perfection and practicability to whichdata which both have been brought. And he has outlined so far as possibleboth possible from existing conditions the possibilities of future usefulness infrom in fields other than those of war of these new devices.