No two sorts of birds practise quite the same sort of flight; the varieties are infinite; but two classes may be roughly seen. Any shi that crosses the Pacific is accompanied for many days by the smaller albatross, Which may keep company with the vessel for an hour without visible or more than occasional movement of wing. The currents of air that the walls of the ship direct upwards, as well as in the line of its course, are enough to give the great bird with its immense wings sufficient sustenance and progress. The albatross is the king of the gliders, the class of fliers which harness the air to their purpose, but must yield to its opposition. In the contrary school, the duck is supreme. It comes nearer to the engines with which man has 'conquered' the air, as he boasts. Duck, and like them the pigeons, are endowed with such-like muscles, that are a good part of the weight of the bird, and these will ply the short wings with such irresistible power that they can bore for long distances through an opposing gale before exhaustion follows.

 

Their humbler followers, such as partridges, have a like power of strong propulsion, but soon tire. You may pick them up in utter exhaustion, if wind over the sea has driven them to a long journey. The swallow shares the virtues of both schools in highest measure. It tires not, nor does it boast of its power; but belongs to the air, travelling it may be six thousand miles to and from its northern nesting home, feeding its flown young as it flies, and slipping through we no longer take omens from their flight on this side and that; and even the most superstitious villagers no longer take off their hats to the magpie and wish it good-morning.

 

沒有任何兩種鳥的飛行方式是相同的。鳥的飛行方式千差萬別，但大體上可分為兩類。任何一艘橫度太平洋的輪船都會有一種小信天翁伴隨飛行許多天。它們隨船飛行一小時也難得見其扇動一下翅膀。沿船體的上升的氣流和沿航線向前的氣流給這種巨翼大鳥以足夠的浮力和推力。信天翁是滑翔飛行的鳥類之王，它能自如地駕馭空氣，但必須順氣流飛行。與滑翔鳥相對的另一類鳥中，數野鴨本領最高。它更近乎于人類自夸的“征服”了空氣的發動機。野鴨及它們相似的鴿子有天賦的鋼鐵般的肌肉，占了體重的很大一部分。這些肌肉以巨大的力量扇動短小的翅膀，使這類鳥能頂著大風飛行很遠的路才會疲勞。

 

次于野鴨和鴿子的鳥，如鷓鴣，有相似的巨大推動力，但很快會疲勞。如果海風驅使它們飛行很長距離，你可以撿到一些因筋疲力盡而摔下來的鷓鴣。燕子充分兼有這兩類鳥的長處，它既不疲勞，也不炫耀自己的飛翔力；在空中十分自如，可以飛行6，000英里，可以飛往北方做窩的老家，再從老家飛回；一邊飛一邊喂養會飛的雛燕，甚至在頂風時也能在氣流中滑翔，似乎氣流在幫它前進。這些鳥對我們是有益的，雖然我們不再從它們的飛翔姿態來占卜吉兇，連最迷信的村民也不再對喜鵲脫帽行禮，祝它早安了。