Aircraft and Submarines

"...Not since gunpowder was first employed in warfare has so revolutionary a contribution to the science of slaughtering men been made as by the perfection of aircraft and submarines. The former have had their first employment in this world-wide war of the nations. The latter, though in the experimental stage as far back as the American Revolution, have in this bitter contest been for the first time brought to so practical a stage of development as to exert a really appreciable influence on the outcome of the struggle. Comparatively few people appreciate how the thought of navigating the air's dizziest heights and the sea's gloomiest depths has obsessed the minds of inventors. From the earliest days of history men have grappled with the problem, yet it is only within two hundred years for aircraft and one hundred for submarines that any really intelligent start has been made upon its solution. The men who really gave practical effect to the vague theories which others set up—in aircraft the Wrights, Santos-Dumont, and Count Zeppelin; in submarines Lake and Holland—are either still living, or have died so recently that their memory is still fresh in the minds of all..."