It is not unlikely that phenomena of a new and different description from any we have hitherto observed, may be produced from the same causes to which we have adverted. A certain optical writer remarks--‘If the variation of the refractive power of the air takes place in a horizontal line perpendicular to the line of vision, that is, from right to left, then we may have a _lateral_ Mirage, that is, an image of a ship may be seen on the right or left hand of the real ship, or on both, if the variation of refractive power is the same on each side of the line of vision, and a fact of this kind was once observed on the Lake of Geneva. If there should happen at the same time, both a vertical and a lateral variation of refractive power in the air, and if the variation should be such as to expand or elongate the object in both directions, then the object would be magnified as if seen through a telescope, and might be seen and recognized at a distance at which it would not otherwise have been visible. If the refracting power, on the contrary, varied, so as to construct the object in both directions, the image of it would be diminished as if seen through a concave lens.’
_Remarks and Reflections, in reference to the phenomena described above._
Such, then, are some of the striking and interesting effects produced by the refraction and the reflection of the rays of light. As the formation of the _images_ of objects by convex lenses, lays the foundation of the construction of refracting telescopes and microscopes, and of all the discoveries they have brought to light, so the property of _concave specula_, in forming similar images, is that on which the construction of _Reflecting_ telescopes entirely depends. To this circumstance Herschel was indebted for the powerful telescopes he was enabled to construct--which were all formed on the principle of reflection--and for all the discoveries they enabled him to make in the planetary system, and in the sidereal heavens. The same principles which operate in optical instruments, under the agency of man, we have reason to believe, frequently act on a more expansive scale in various parts of the system of nature. The magnificent _Cross_ which astonished the preacher and the immense congregation assembled at Migné, was, in all probability, formed by a vast atmospherical speculum formed by the hand of nature, and representing its objects on a scale far superior to that of human art; and probably, to the same cause is to be attributed the singular phenomenon of the coast of France having been made to appear within two or three miles of the town of Hastings, as formerly described, (see p. 53.) Many other phenomena which we have never witnessed, and of which we can form no conception, may be produced by the same cause operating in an infinity of modes.