"Diamond X!" he murmured. "That isn't our ranch! Our bunk house isn't so near the corral, and, besides——"
Then, even as he spoke, this vision vanished as had the other, being wiped out of sight; fading slowly as if some unseen operator in a movie booth had cut off his light.
The brothers turned and stared at one another. Suddenly the truth dawned upon them.
"A mirage!" exclaimed Nort.
"That's what!" assented Dick. "Two mirages! We saw one after the other, a city and a ranch in the same place!"
And that is what the visions had been—mirages, those strange phenomena of the west—of desert places—natural occurrences in localities where the air is abnormally clear, and where conditions combine to transpose distant scenes.
Of course the explanation is simple enough. Of the mirage the dictionary says it is "an optical illusion arising from an unequal refraction in the lower strata of the atmosphere, causing images of remote objects to be seen double, distorted or inverted as if reflected in a mirror, or to appear as if suspended in the air."
The word comes from a Latin one, meaning "to look at," and that is about all you can do to a mirage—look at it. It is as unsubstantial as the air in which it is formed.
There are many varieties of mirages seen in the West, and if the boys had seen a double one, or had the vision of the city and ranch been inverted, they might have sooner guessed the secret of it. But the particular mirages they had viewed had, through some trick of air refraction, been imposed on their eyesight rightside up, and wonderfully clear.
I do not suppose all the stories that have been written of mirages are true, but it is certain that many strange tricks have been played on the eyesight of observers by these phenomena, and more than one luckless prospector, or cattleman, has followed these visions, only to be tantalized in the end by finding, just as Nort and Dick did, that they merely vanished, dissolving into nothing.