over the valley beyond. As such shadows were very faint, they were considered distant, and therefore seemed men walking on the opposite ridge; and because a comparatively small figure seen near, but supposed to be distant, appears of gigantic size, these shadows were accounted giants.

Dr. Buchan mentions a similar effect. 66 'Walking on the cliff," he says, "about a mile to the east of Brighton, on the morning of the 18th of November, 1804, while watching the rising of the sun, I turned my eyes directly towards the sea, just as the solar disc emerged from the surface of the water, and saw the face of the cliff on which I was standing represented precisely opposite to me at some distance from the ocean. Calling the attention of my companion to this appearance, we soon also discovered our own figures standing on the summit of the opposite apparent cliff, as well as the representation of a windmill near at hand. The reflected images were most distinct precisely opposite to where we stood, and the false cliff seemed to fade away, and to draw near to the real one, in proportion as it receded towards the west. This phenomenon lasted about ten minutes, till the sun had risen nearly his own diameter above the sea. The whole then seemed to be elevated into the air, and successively disappeared.

EFFECT OF A FOG.

79

The surface of the sea was covered with a dense fog of many yards in height, and which gradually receded before the rays of the sun."

It is hoped that the explanation now given will not only satisfy the mind as to the phenomena described, but that it will prevent any erroneous impression in reference to others of a similar kind.

CHAPTER VII.

COLOURS THE RAINBOW-VISION OF JOHN IN PATMOS.

WE are little aware, until engaged in serious reflection, how great a difference would arise were only one alteration made in the arrangements of the great Creator. Had, for instance, a white light fallen on the objects around us, and had they been equally acted upon by the bodies on which they fall, all the objects of the material world would then have had a leaden hue. In this case, it has been truly said, all the features of the human countenance would have presented no other variety than they have in a pencil sketch or a China ink drawing ; the rainbow would have dwindled into a narrow arch of white light; the stars would have shone through a grey sky, and the mantle of a wintry twilight would have replaced the golden robe of the setting sun.

A curious illustration of this fact will appear in illuminating objects with light of one colour. If we cast a pure and unmixed yellow light on scarlet cloth, it will appear yellow, because the scarlet cloth does not absorb

LIGHT OF ONE COLOUR.

81

all the yellow rays, but reflects some of them; and if we illuminate blue cloth with yellow light, it will appear nearly black, because it absorbs nearly all the yellow light, and reflects scarcely any of it. But whatever be the nature and colour of the bodies on which the yellow light falls, the light which it reflects must be yellow, since they have no other light; and those which are not capable of reflecting yellow light must appear absolutely black, however brilliant be their colour in the light of day.

It has been long known that salt thrown into the wick of a flame produces yellow light, but this is mixed with blue and green rays, and is, besides, small in quantity. An apparatus has therefore been constructed for a curious experiment, and the effect is thus described by Sir David Brewster :-" Having obtained the means of illuminating any apartment with yellow light, let the exhibition be made in a room with furniture of various bright colours, and with oil or water-coloured paintings on the wall. The party which is to witness the experiment should be dressed in a diversity of the gayest colours; and the brightest coloured flowers and highly coloured drawings should be placed on the tables. The room being at first lighted with ordinary lights, the bright and gay colours of every thing that it contains will be finely

G

displayed. If the white lights are now suddenly extinguished, and the yellow lamps lighted, the most appalling metamorphosis will be exhibited. The astonished indi

viduals will no longer be able to recognize each other. All the furniture in the room, and all the objects which it contains, will exhibit only one colour. The flowers will lose their hues; the paintings and drawings will appear as if they were executed in China ink; and the gayest dresses, the brightest scarlets, the purest lilacs, the richest blues, and the most vivid greens, will all be converted into one monotonous yellow. The complexions of the parties too will suffer a corresponding change. One pallid, death-like yellow,

Like the unnatural hue

Which autumn paints upon the perished leaf,'

will envelop the young and the old, and the sallow face will alone escape from the metamorphosis. Each individual derives merriment from the cadaverous appearance of his neighbour, without being sensible that he is one of the ghastly assemblage."

Had there been light without the distinction of colours, objects could only have been distinguished by circumstances of time, place, or relative position; or by intricate trains of reasoning. To what perplexities and