The snowfields on high ranges of mountains are of a dazzling whiteness; and their bright glare is so great as to distress the eyes of those who walk over them without blue glasses, and even to cause inflammation. At these heights the traveller is not only exposed to the direct rays of the sun, untempered save for a thin veil of rarefied air, but also to an intense glare produced by the little snow-crystals which scatter around the beams of light falling upon them. Scientific men, who have studied these matters, say that the scorching of the skin and "sun-burning" experienced by Alpine travellers is not caused, as might be supposed, by the heat of the sun, but by the rays of light darting and flashing on all sides from myriads of tiny snow-crystals. Occasionally a soft lambent glow has been observed on snowfields at night. This is a very curious phenomenon, to which the name of "phosphorescence" has, rightly or wrongly, been given. A pale light may often be seen on the sea during a summer night, when the water is disturbed in any way; and if one is rowing in a boat, the oars seem glowing with a faint and beautiful light. It is well known that this is caused by myriads of little light-producing animalcules in the sea-water. But we can hardly suppose that the glow above referred to is produced by a similar cause. One observer says the glow is "something like that produced by the flame of naphtha;" and he goes on to say that at every step "an illuminated circle or nimbus about two inches in breadth surrounded our feet, and we seemed to be ploughing our way through fields of light, and raising clods of it, if I may be allowed the expression, in our progress." Another observer, also an Alpine traveller, says that at almost every footstep the snowy particles, which his companion in front lifted with his feet from the freshly fallen snow, fell in little luminous showers. The exact cause which produces this strange effect at night has not been ascertained. There is another curious phenomenon often seen just before sunset on a mountain in Hungary. It is known as "The Spectre of the Brocken." The Brocken is the highest summit of the Hartz Mountains. As you step out upon the plateau upon the top of the hill, your shadow, grim and gigantic, is apparently flung right out against the eastern sky, where it flits from place to place, following your every movement. The explanation is simply this: to the east of the Hartz Mountains there is always a very dense and hazy atmosphere, so dense that it presents a surface capable of receiving the impression of a shadow, and of retaining it, as a wall does. The shadows are really close at hand, not a long way off, as might at first sight be supposed. If very far away, they would be too faint to be visible.