Such aërial surveys form an important use for both the smaller types of airships, aëroplanes, and hydroplanes. When more records come to hand than it is now possible to obtain in regard to naval doings in the present war it will be interesting to observe the amount of actual work that has been done in detecting submarines and the other hidden dangers in the sea. CHAPTER XI PRESENT DEFICIENCIES AND FUTURE POSSIBILITIES OF THE MILITARY AËROPLANE In the portion of this handbook which especially dealt with airships, certain advantages possessed by them over aëroplanes were noted; several of their disadvantages were also a matter of comment. It was hinted that in the future it might be possible to impart to aëroplanes also those very advantages of which the airship can still certainly make boast. Should this be done by engineering skill--and it is well within the limits of reasonable possibility--then it would seem that the lighter-than-air machine must entirely yield its claim as an adjunct of war to the heavier-than-air principle. The free balloon “mounting heavenwards,” as Carlyle said, “so beautifully, so unguidably,” is now merely a past reminiscence, and even so, too, will be the mammoth motor-impelled gas envelopes. When the din of war ceases, the still greater perfection of the aëroplane should be the object of the attention of British engineering skill. The endowment of the aëroplane with certain qualities in which it is still deficient appears to be merely a matter of engineering detail based on principles that have been already elucidated. Since the brothers Wright made their epoch motor flights which gave to man the attribute of the bird, so long his envy, progress in flight records has been largely made in the attempt to win a money prize. In one sense the pilot has progressed at a faster rate than has the evolution of the machine. He has accomplished heights, durations, and distances on machines in which the margin of safety is indeed small. It might be well if the next series of prizes should be devoted to the further development of the machine itself--prizes which would, in their turn, stimulate the genius of the aëronautical engineer. Four essential points in the future development of flying machines are:-- 1. Variable speed. 2. Immediate rising into the air. 3. Hovering in the air. 4. Stability. 1. _Variable speed._ The aërial machine that cannot vary its speed, so as to be able to go fast, at moderate pace, or quite slow, must from one point of view be in a crude state of development. Yet aëroplanes are as yet in this stage of growth.