When travelling by night, I have frequently been struck with the behaviour of my horse at the sight of natural fire, or appearance of fire, always so different from that caused by the sight of fire artificially created. The steady gleam from the open window or door of a distant house, or even the unsteady wind-tossed flame of some lonely camp-fire, has only served to rouse a fresh spirit in him and the desire to reach it; whereas those infrequent displays of fire which nature exhibits, such as lightning, or the ignis fatuus, or even a cloud of fireflies, has always produced a disquieting effect. Experience has evidently taught the domestic horse to distinguish a light kindled by man from all others; and, knowing its character, he is just as well able as his rider to go towards it without experiencing that confusion of mind caused by a glare in the darkness, the origin and nature of which is a mystery. The artificially-lighted fire is to the horse only the possible goal of the journey, and is associated with the thought of rest and food. Wild animals, as a rule, at any rate in thinly-settled districts, do not know the meaning of any fire; it only excites curiosity and fear in them; and they are most disturbed at the sight of fires made by man, which are brighter and steadier than most natural fires. We can understand this sensation in animals, since we ourselves experience a similar one (although in a less degree and not associated
Nature's Night Lights. 175
with fear) in the effect which mere brightness has on us, both by day and night.
On riding across the monotonous grey Patagonian uplands, where often for hours one sees not the faintest tinge of bright colour, the intense glowing crimson of a cactus-fruit, or the broad shining white bosom of the Patagonian eagle-buzzard (Buteo erythronotus), perched on the summit of a distant bush, has had a strangely fascinating effect on me, so that I have been unable to take my eyes off it as long as it continued before me. Or in passing through extensive desolate marshes, the dazzling white plumage of a stationary egret has exercised the same attraction. At night we experience the sensation in a greater degree, when the silver sheen of the moon makes a broad path on the water; or when a meteor leaves a glowing track across the sky; while a still more familiar instance is seen in the powerful attraction on the sight of glowing embers in a darkened room. The mere brightness, or vividness of the contrast, fascinates the mind; but the effect on man is comparatively weak, owing to his fiery education and to his familiarity with brilliant dyes artificially obtained from nature. How strong this attraction of mere brightness, even where there is no mystery about it, is to wild animals is shown by birds of prey almost invariably singling out white or bright-plumaged birds for attack where bright and sober-coloured kinds are mingled together. By night the attraction is immeasurably greater than by day, and the light of a fire steadily gazed at quickly confuses the mind. The fires which, travellers make
176 The Naturalist in La Plata.
for their protection actually serve to attract the beasts of prey, but the confusion and fear caused by the bright glare makes it safe for the traveller to lie down and sleep in the light. Mammals do not lose their heads altogether, because they are walking on firm ground where muscular exertion and an exercise of judgment are necessary at every step; whereas birds floating buoyantly and with little effort through the air are quickly bewildered. Incredible numbers of migratory birds kill them-selves by dashing against the windows of lighthouses; on bright moonlight nights the voyagers are comparatively safe; but during dark cloudy weather the slaughter is very great; over six hundred birds were killed by striking a lighthouse in Central America in a single night. On insects the effect is the same as on the higher animals: on the ground they are attracted by the light, but keep, like wolves and tigers, at a safe distance from it; when rushing through the air and unable to keep their eyes from it they fly into it, or else revolve about it, until, coming too close, their wings are singed.
I find that when I am on horseback, going at a swinging gallop, a bright light affects me far more powerfully than when I am trudging along on foot. A person mounted on a bicycle and speeding over a level plain on a dark night, with nothing to guide him except the idea of the direction in his mind, would be to some extent in the position of the migratory bird. An exceptionally brilliant ignis fatuus flying before him would affect him as the gleam of a lamp placed high above the surface