A letter from a correspondent in New Zealand, dated Nelson, September 15, 1857, contains the subjoined passages:—“Even in summer people here have no notion of going without fires in the evening; but then, though the days are very warm and sunny, the nights are always cold. For seven months last summer we had not one day that the Sun did not shine as brilliantly as it does in England in the finest day in June; and though it has more power here, the heat is not nearly so oppressive.... But then there is not the twilight which you get in England. Here it is light till about eight o’clock; then, in a few minutes, it becomes too dark to see anything, and the change comes over in almost no time.” “Twilight lasts but a short time in so low a latitude as 28 degrees, and no sooner does the Sun peep above the horizon, than all the gorgeous parade by which he is preceded is shaken off, and he comes in upon us in the most abrupt and unceremonious way imaginable.”[9] These various peculiarities could not exist in the southern region if the Earth were spherical and moved upon axes, and in an orbit round the Sun. If the Sun is fixed, and the Earth revolves underneath it, the same phenomena should exist at the same distance on each side of the Equator. But such is not the case! What can operate to cause the twilight in New Zealand to be so much more sudden than it is in England? The southern “hemisphere” cannot revolve more rapidly than the northern! The distance round a globe would be the same at 50° south as at 50° north, and as the whole globe would revolve once in 24 hours, the surface at the two places would move underneath the Sun with the same velocity, and the light would approach in the morning and recede in the evening in exactly the same manner; yet the very contrary is the fact! The twilight in England in summer is slow and gradual, but in New Zealand it is rapid and abrupt; a difference which is altogether incompatible with the doctrine of the Earth’s rotundity. But, the Earth a plane, and it is a simple “matter of course.” Let E, in [Figure 28], represent England, and W New Zealand; the radius N E and the consequent circle round N is much less than the radius N W and its consequent circle round the same point. But as the larger circle, radius N W is passed over by the sunlight in the same time (24 hours) as the smaller circle, radius N E, the velocity is proportionately greater. The velocity is the space passed over multiplied by the time in passing, and as the space over New Zealand is much greater than the space over England, the velocity of the Sun-light must be much greater, and its morning and evening twilight necessarily more “abrupt and unceremonious;” and therefore, it might be said with strictly logical accuracy, the Earth is a Plane, and cannot possibly be a Globe!
[9] Captain Basil Hall, R.N., F.R.S.
SECTION 7.
CAUSE OF “SUNRISE” AND “SUNSET.”
FIG. 29.
Although the Sun is at all times above and parallel to the Earth’s surface, he appears to ascend the firmament from morning until noon, and to descend and sink below the horizon at evening. This arises from a simple and everywhere visible law of perspective. A flock of birds, when passing over a flat or marshy country, always appears to descend as it recedes; and if the flock is extensive, the first bird appears lower, or nearer to the horizon than the last. When a balloon sails from an observer without increasing or decreasing its altitude, it appears gradually to approach the horizon. The farthest light in a row of lamps appears the lowest, although each one has the same altitude. Bearing these phenomena in mind, it will easily be seen how the Sun, although always parallel to the surface of the Earth, must appear to ascend when approaching, and descend after leaving the meridian or noon-day position. Let the line A B, [Fig. 29], represent a portion of the Earth’s surface; C D of the Sun’s path, and H H, the line of sight. The surface of the Earth, A B, will appear to ascend from B to H, forming the horizon. When the Sun is traversing the line C D, in the direction of the arrows, he will appear to emerge from the horizon H, and to gradually ascend the line H D. When in the position 1, he will appear to be at the point 2; and when at 3, the apparent position will be at 4; but when he arrives upon the meridian D, his apparent and actual, or noon-day position, will be the same. But now, from the point D, the Sun will appear to descend, as in [Fig. 30], and when he has passed from D to 1, he will appear at 2, and when really at 3 will appear at 4; and thus continuing his course in the direction D C, he will reach the horizon at H, and disappear or “set” to the observer at H A. Thus “Sunrise” and “Sunset” are phenomena dependent entirely upon the fact that horizontal lines parallel to each other appear to approach or converge in the distance, the surface of the Earth being horizontal, and the line-of-sight of the observer and the Sun’s path being parallel with it, necessarily produce the observed phenomena.
FIG. 30.
SECTION 8.
CAUSE OF SUN APPEARING LARGER WHEN RISING AND SETTING THAN WHEN ON THE MERIDIAN.
It is well known that when a light of any kind shines through a dense medium it will appear larger than when seen through a lighter medium. This will be more remarkable when the medium holds aqueous particles in solution,—as in a damp or foggy atmosphere the light of a gas-lamp will seem greater at a given distance than it will under ordinary circumstances. In the diagram, [Figure 30], it is evident that H D is less than H 1, H 3, or H 5. The latter (H 5) represents the greater amount of atmosphere which the Sun has to shine through when approaching the horizon; and as the air near the Earth is both more dense and more damp, or holds more watery particles in solution, the light of the Sun must be dilated or enlarged as well as modified in colour. But the enlarged appearance of the Sun when rising and setting is only an optical impression, as proved by actual measurement. “If the angle of the Sun or Moon be taken either with a tube or micrometer when they appear so large to the eye in the horizon, the measure is identical when they are in the meridian and appear to the eye and mind but half the size. The apparent distance of the horizon is three or four times greater than the zenith. Hence the mental mistake of horizontal size, for the angular dimensions are equal; the first 5° is apparently to the eye equal to 10° or 15° at 50° or 60° of elevation; and the first 15° fill a space to the eye equal to a third of the quadrant. This is evidently owing to the ‘habit of sight,’ for with an accurate instrument the measure of 5° near the horizon is equal to 5° in the zenith.”[10]