If the humming bird will not serve, look above you. There rides the dark-winged master of aërial motion, throned like a god on the impetuous wind. Mark his majestic sweep as all day long, with unbeating pinion, he scours the wide plain and rugged regions of the hills, unwearied, reposeful, deliberate; now skimming the fragrant forest, or meadow; now scaling the precipice, or swinging above the abyss; now soaring cloudward beyond the range of human vision. There is a model for the ambitious and the brave! Or turn to mid ocean when the hurricane, shearing the tops of the arched billows, scatters them in foam and spray over the watery chaos, and the big ship strains in the storm. See the long-winged albatross, white vision of joy in the darkness, careering all playfully round the imperiled vessel, and above the monstrous waves; wheeling in glad curves, frolicking in the face of the tempest, riding, without toil or trepidation, the rudest[19] winds a thousand miles over the sea. What a jocund pace for man! Of all the charming modes of flight now possible to us it is certain that our ancestors could copy but one with any hope of success. Minus motive power they could not imitate the direct flight of the homing pigeon, much less the mid-air pause of the bumblebee floating round a daisy. Hence there remained to them only passive flight on nonvibrant wings. The gliding of vultures, of gulls, and of certain quadrupeds and fishes, they could imitate with profit; but when they essayed power flight they invariably and egregiously failed. The art of aviation presents two main groups of fliers. The first comprises the various man kites, parachutes, gliding machines, soaring machines. These may be called passive flyers, because they carry no motive power, but ride passively on the air by the force of gravity or a towline. The second group comprises the bird-like flap-wing machines, called orthopters by technical people; the screw-lift flyers, called helicopters; the aëroplanes, also called monoplanes, biplanes, triplanes, according to the number of superposed main lifting surfaces; and lastly the gyroplanes, whose sustaining surfaces may turn over and over, like a falling lath, or whirl round and round, like a boomerang. These all may be called dynamic, or power, flyers. The technical names, however, are not so important, as they are numerous; for the whole aëronautic nomenclature is in a formative, not to say chaotic, state. We may, therefore, like Adam, name the creatures as they pass before us for review or discussion.