396 REPORTS ON THE STATE OF SCIENCE, ETC. 
left for Aeronautics to examine the effects of compressibility,—for pro- 
jectiles have long been discharged at speeds exceeding that of sound. But 
the special theories, the new technique, which are the contribution of 
Aeronautics have come to lead, rather than to follow, the attack on these 
older problems ; and for that reason it seems fair to speak of the science 
as Aerodynamics, even at some cost in accuracy. 
* Applied Aerodynamics ’. 
I shall attempt to-night a brief review of aeronautical progress from 
a particular standpoint,—the standpoint of science ; and in the main it is 
with this new science of Aerodynamics that I shall be concerned. Not with 
Aerodynamics as a pure science,—the ‘ theoretical hydrodynamics ’ of the 
mathematician and physicist,—for that is old ; but with “ Applied Aero- 
dynamics ’,—that is, with the science in its definite modern orientation, an 
orientation which has been determined by the ambition of man to fly. 
Just as the whole development of applied electricity was conditioned by the 
fact that man (unlike Nature) can best utilise a source of power which 
rotates, so the course of applied aerodynamics has been conditioned by the 
fact that man has elected to build his aeroplanes ‘ just so’. 
Historical Study in Science. 
3. There is always fascination in the study of a science from the 
historical standpoint ; in seeing how tentative and isolated advances— 
some made with immediate success, others in the face of difficulties only 
surmounted after the lapse of years—have eventually met and coalesced, 
with the gain of some definite addition to knowledge. The fascination is 
even greater, perhaps,—certainly the story tends to be more complicated,— 
when the science is * applied ’, because of this interaction between science 
(properly pursued for its own interest) and technical development (properly 
pursued for its own ends). Pure sciences seem to develop, like some natural 
growth, along orderly and logical lines: a new and revolutionary dis- 
covery may impair, for the moment, the symmetry of the structure ; but 
immediately a process of bridging—of ‘cross-connection’—begins. Applied 
sciences, by comparison, have more likeness to a military campaign. 
Sometimes there is a halt in the advance, while the existing position is 
strengthened and reserves of accurate and co-ordinated knowledge are 
accumulated: at others, these reserves are expended in a supreme and 
sustained effort, and technical advance is carried up to, or even beyond, 
any position which could be—in the military phrase— consolidated’, 
Its Special Importance for Aeronautics. 
In Aeronautics—the latest of the applied sciences—this campaign has 
been brief in years, brilliant in its achievement. It is little more than 
twenty years since the Wright brothers made their first power-driven 
flight (it did not last one minute) in North Carolina; less than twenty 
years since Santos Dumont astonished the world by flying a distance of 60 
metres against the wind: yet by now an aeroplane has carried its pilot 
to a height of 74 miles, an aeroplane has been flown at a speed of nearly 
