WHEN WE MUST NOT BELIEVE OUR EYES.
There are a great number of marvellous things told us of phantom forms and ghostly apparitions—of spectres that flit about lonely roads on moonlight nights, or haunt peaceful people in their own homes; of funeral processions, with long trains of mourners, watched from a distance, but which, on nearer approach, melt into a line of mist; of wild witch-dances in deserted houses, and balls of fire bounding out of doors and windows—stories which cause the flesh of children to creep upon their bones, and make cowards of them where there is no reason for fear. For you may lay it down as a fact, established beyond dispute, that not one of these things is a reality. The person who tells these marvels has always what seems the best of reasons for his belief. He either saw these things himself or knew somebody, strictly truthful, who had seen them. He did not know, what I am going to prove to you, that a thing may be true and yet not be real. In other words, that there are times when we do actually see marvels that seem supernatural, but that, on such occasions, we must not believe our own eyes, but search for a natural cause, and, if we look faithfully, we are sure to find one.
Once a vessel was sailing over a northern ocean in the midst of the short, Arctic summer. The sun was hot, the air was still, and a group of sailors lying lazily upon the deck were almost asleep, when an exclamation of fear from one of them made them all spring to their feet. The one who had uttered the cry pointed into the air at a little distance, and there the awe-stricken sailors saw a large ship, with all sails set, gliding over what seemed to be a placid ocean, for beneath the ship was the reflection of it.
The news soon spread through the vessel that a phantom-ship with a ghostly crew was sailing in the air over a phantom-ocean, and that it was a bad omen, and meant that not one of them should ever see land again. The captain was told the wonderful tale, and coming on deck, he explained to the sailors that this strange appearance was caused by the reflection of some ship that was sailing on the water below this image, but at such a distance they could not see it. There were certain conditions of the atmosphere, he said, when the sun's rays could form a perfect picture in the air of objects on the earth, like the images one sees in glass or water, but they were not generally upright, as in the case of this ship, but reversed—turned bottom upwards. This appearance in the air is called a mirage. He told a sailor to go up to the foretop and look beyond the phantom-ship. The man obeyed, and reported that he could see on the water, below the ship in the air, one precisely like it. Just then another ship was seen in the air, only this one was a steamship, and was bottom-upwards, as the captain had said these mirages generally appeared. Soon after, the steamship itself came in sight. The sailors were now convinced, and never afterwards believed in phantom-ships.
A French army marching across the burning sands of an Egyptian desert, fainting with thirst and choked with fine sand, were suddenly revived in spirit by the sight of a sheet of water in the distance. In it were mirrored the trees and villages, gardens and pretty houses of a cultivated land, all reversed. The blue sky was mirrored there, too, just as you can see the banks of a lake, and the sky that bends over it, in its calm waters. The soldiers rushed towards the place, frantic with joy, but when they got there they found nothing but the hot sands. Again they saw the lake at a distance, and made another headlong rush, only to be again disappointed. This happened frequently, until the men were in despair, and imagined that some demon was tormenting them. But there happened to be with this army a wise man, who did not trust entirely to his own eyes, and although he saw exactly what the others did, he did not believe that there was anything there but air. He set to work to investigate it, and found out that the whole thing was an illusion—it was the reflection of the gardens and villages that were on the river Nile, thrown up into the air, like the ships the sailors saw, only in the clear atmosphere of Egypt these images are projected to a long distance. And demons had nothing whatever to do with it.
People used to believe in a fairy called Fata Morgana. Wonderful things were said of her, and her dominions were in the air, where she had large cities which she sometimes amused herself by turning into a variety of shapes. The cities were often seen by dwellers on the Mediterranean sea-coast. Sometimes one of them would be like an earthly city, with houses and churches, and nearly always with a background of mountains. In a moment it would change into a confused mass of long colonnades, lofty towers, and battlements waving with flags, and then the mountains reeling and falling, a long row of windows would appear glowing with rainbow colors, and perhaps, in another instant, all this would be swept away, and nothing be seen but gloomy cypress trees.