PDF - Wallace Online

i CLIMATE AND ASPECTS OF THE EQUATORIAL ZONE 233that of the tropics. Even with us the duration of twilightis very much shorter at the time of the equinoxes, andit is probably not much more than a third shorter than thisat the equator. Travellers usually exaggerate the shortnessof the tropical twilight, it being sometimes said that ifwe turn a page of the book we are reading when thesun disappears, by the time we turn over the next pageit will be too dark to see to read. With an average bookand an average reader this is certainly not true, and itwill be well to describe as correctly as we can what reallyhappens.In fine weather the air appears to be somewhat moretransparent near the equator than with us, and the intensityof sunlight is usually very great up to the moment when thesolar orb touches the horizon. As soon as it has disappearedthe apparent gloom is proportionally great, but this hardly increasesperceptibly during the first ten minutes. During thenext ten minutes, however, it becomes rapidly darker, and atthe end of about half an hour from sunset the complete darknessof night is almost reached. In the morning the changes areperhaps even more striking. Up to about a quarter past fiveo'clock the darkness is complete ;but about that time a fewcries of birds begin to break the silence of night, perhapsindicating that signs of dawn are perceptiblein the easternhorizon. A little later the melancholy voices of the goatsuckersare heard, varied croakings of frogs, the plaintivewhistle of mountain thrushes, and strange cries of birds ormammals peculiar to each locality.About half-past five thefirstglimmer of light becomes perceptible ; it slowly becomeslighter, and then increases so rapidly that at about a quarterto six it seems full daylight. For the next quarter of anhour this changes very little in character ; when, suddenly, thesun's rim appears above the horizon decking the dew-ladenfoliage with glittering gems, sending gleams of golden lightfar into the woods, and waking upall nature to life andactivity. Birds chirp and flutter about, parrots scream,monkeys chatter, bees hum among the flowers, and gorgeousbutterflies flutter lazily along or sit with fully expandedwings exposed to the warm and invigorating rays. The firsthour of morning in the equatorial regions possesses a charm