Persons who insist on explaining various phenomena, such as the one described in Chapter 3, as due to mirage effects, certainly do not stop to consider the weakness of their arguments. I have been doing a great deal of research work on the subject of mirages and have come to a definite conclusion that they cannot be explained by atmospheric refraction and reflection as maintained by all modern writers of scientific text-books. Furthermore, I have come to the more important conclusion that the mirage furnishes direct and unmistakable evidence of the earth's concavity.
It is a matter of common experience that the so-called mirage does take place; and since the prevailing theory of the earth's form requires that the actual position of distant objects shall be below the observer's horizon (and therefore invisible), when at times such objects are distinctly seen to be above the horizon, it is obviously necessary to frame up some such hypothesis as atmospheric refraction to account for the phenomenon.
Before proceeding to a discussion of the commonly accepted explanation of the mirage I will present here a few records of observations that I have come across in my research work. The reader should bear in mind the pictures of the "inundation," and other effects, when he comes to read my chapter on the Disappearance of Vessels.
It is indeed remarkable that the same phenomena which I myself have repeatedly observed to occur over the surface of water, have also been observed over land surfaces, and their records have come down to us as authoritative evidence of the earth's concavity.
Chambers, in his "Information for the People," gives the following account, viz.: "In the sandy plains of Egypt, the mirage is seen to great advantage. These plains are often interrupted by small eminences, upon which the inhabitants have built their villages, to escape the inundations of the Nile.
In the morning and evening objects are seen in their natural form; but when the surface of the sandy ground is heated by the sun, the land seems terminated at a particular distance by a general inundation; the villages which are beyond it appear like so many islands in a great lake, and between each village an inverted image of it is seen."
Mary Somerville, in "The Connection of the Physical Sciences," records the following: "When extraordinary refraction takes place laterally, the strata of variable density are perpendicular to the horizon, and if combined with vertical refraction, the objects are magnified as when seen through a telescope. From this cause, on the 26th of July, 1798, the cliffs of France, fifty miles off, were seen distinctly from Hastings as if they had been close at hand; and even Dieppe was said to have been visible in the afternoon."
Lardner's "Handbook of Natural Philosophy and Astronomy" contains the following: "Various fantastical optical effects of this kind are recorded as having been observed during the campaign of the French army in Egypt. On this occasion, a corps of savants accompanied the army, in consequence of which, the particulars of the phenomena were accurately observed and explained. When the surface of the sands was heated by the sun, the land seemed terminated at a certain point by a general inundation. Villages were seen standing at elevated points like islands in the middle of a lake, and under each village appeared an inverted image of it. As the spectator approached the boundary of the apparent inundation, the waters seemed to retire, and the same illusion appeared round the next village."
The French writer Pouchet gives us the following most interesting account in his book "The Universe" (1877): "It is in the sand deserts that the phenomenon of the mirage takes place most frequently. I was enabled to see it once in all its splendour. "The captain or reis of our escort had asked leave to stay at a part of the Nile where stood one of his harems, in order to pass the day there with his wives and family. I say one, for he had several, ingeniously established along the river, the scene of the continual voyages which he made. He stopped by successive stages at each of his establishments, in such a way as not to excite the jealousy of any of the sultanas whom he maintained.
"I had profited by this halt to make an excursion into the desert, and had started when the reis, seeing me in the distance, came with some Arabs of his tribe to beg I would accept the hospitality of his roof. In the East to refuse such an offer would be almost an offence, so I turned towards the oasis which he inhabited. It was a delicious hamlet, crowned with date-trees, and the entrance to it was picturesquely decorated with some tombs of a most charming appearance.
"After the frugal repast of dates and milk which was offered me, I plunged into the desert and I was already at a distance when the idea came into my head to salute this hospitable abode for the last time. But every thing was transformed. The picturesque village seemed enveloped in a magnificent sheet of the most transparent waters in which the dwellings, palm-trees, and tombs were reflected in a marvellous manner. The phenomenon was produced with such exactness, and the sheet of water was so beautiful and limpid, that if I had not a few minutes previously traversed the spot which it occupied on the burning sand, I should have thought it real. Such is the mirage, which so often and so painfully deceived our worn-out soldiers when they traversed these very regions. Exhausted with fatigue and dying of thirst, they thought they saw in the distance the water they longed for so much, while it was only a bitter delusion!"
Now let us see just what the prevailing explanation of the mirage involves. Figure 3E illustrates a portion of the earth's surface supposedly convex. The observer's eye is at the point E. The object D is beyond the horizon H and below the line of sight EH, and is therefore invisible from the point E. Over heated surfaces of the earth such as sandy deserts, it is claimed that the atmosphere near the earth is rarefied in such a manner that a sort of reflecting surface is formed by a layer of air between it and the upper and more dense regions. Rays of light from the object D are bent upwards, as it were, by atmospheric refraction until they reach this reflecting surface, or perhaps to be more scientifically exact, until the critical angle of the rarefied air is reached, at the point A, when they are then reflected down to the point E. Since the rays of light from the object appear to come to the observer in the direction AE, an inverted image of the object is seen at D'.
To explain the virtual, or erect, image, which is seen more often than the inverted one, and is directly over the latter, it is necessary to suppose that the rays of light are made to cross and recross in various ways by atmospheric refraction until the final results appear as actually observed by the eye.
The more I study these "explanations" and the diagrams usually found in school text-books claiming to enlighten the student as to the true cause of the mirage, the more indignant I become to think that such so-called scientific teaching is allowed to go unchallenged. Now if the mirage is due to atmospheric refraction brought about by unusual rarefaction of the air near the earth's surface, we are forced to suppose that the layer of air from which the rays of light are finally reflected to the eye, has become a perfect mirror, for all authentic records of observations show that the mirage images are perfectly clear and distinct. Every portion of the air through which the rays of light pass would have to be heated with perfect uniformity; there could be no irregularities, such as we see on the surface of water when disturbed by the wind thereby greatly distorting the reflection of objects in it. Are such perfect conditions in the atmosphere conceivable? I leave it with the reader to answer the question for himself.
Is it not more reasonable to suppose that distant objects, such as rivers, lakes, cities, etc., appear to be above the horizon simply because they actually are above the horizon, and that these objects become visible, clear and distinct as at times they are observed to be, when the atmosphere near the earth's surface is unusually rarefied? ---
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- -- Source: O. F. Barcus, A New World Discovered (1917).