Chapter VII: Section 6: CAUSE OF DAY AND NIGHT, SEASONS, &c

The Sun S describes the circle A A A on the 21st December once in 24 hours; hence in that period day and night occur to every part of the Earth, except within the Arctic circle. The light of the Sun gradually diminishing from S, to the Arctic circle 1 2 3, where it becomes twilight, does so according to the well-known law of radiation, equally in all directions--hence, the circle 4 5 6 represents the whole extent of the Sun’s light at any given time. The arc 4 E is the advancing or morning twilight, and 6 E the receding or evening twilight; to every place underneath a line drawn across the circle through S to N it is noonday. It will now be easily understood that as the Sun S moves in the direction of the arrows or from right to left, and completes the circle A A A in 24 hours, it will produce in that period morning, noon, evening, and night to all parts of the Earth in succession. On referring to the diagram, it will be seen that to England, E, the length of the day at this time of the year is the _shortest_, the amount of light being represented by the arc E E E; and also that the northern centre N remains in darkness during the whole daily revolution of the Sun, the light of which terminates at the Arctic circle 1 2 3. Thus, morning, noon, evening, midnight, the _shortest_ days, or the Winter season, and the constant or six months’ darkness at the pole are all a part of one general phenomenon. As the Sun’s path begins now to diminish every day until in six months, or on the 15th of June, it describes the circle B B B, it is evident that the same extent of sunlight will reach over or beyond the pole N, as shown in the following diagram (Fig. 28), when morning, noon, evening, and night will again occur as before; but the amount of light passing over England, represented by the arc E E E, is now much larger than when the Sun was upon the circle A A A, and represents the _longest_ days, or the _Summer_ season, and the constant, or six months’ light at the pole. Thus, day and night, long and short days, Winter and Summer, the long periods of alternate light and darkness at the pole, arise simply from the Sun’s position in relation to the north pole.

If the Earth is a globe, it is evident that Winter and Summer, and long and short days, will be of the same character and duration in corresponding latitudes, in the southern as in the northern hemisphere. But we find that in many respects there is a marked difference; for instance, in New Zealand, where the latitude is about the same as in England, a remarkable difference exists in the length of day and night. In the Cook’s Strait Almanack, for 1848, it is stated, “At Wellington, New Zealand, December 21, Sun rises 4h. 31m., and sets at 7h. 29m., the day being 14 hours 58 minutes. June 21st, Sun rises at 7h. 29m., and sets at 4h. 31m., the day being 9 hours and 2 minutes. In England the longest day is 16h. 34m., and the shortest day is 7h. 45m. Thus the _longest day_ in New Zealand is 1 hour and 36 minutes _shorter_ than the _longest day_ in England; and the _shortest day_ in New Zealand is 1 hour and 17 minutes _longer_ than the shortest day in England.”

In a recently published pamphlet, by W. Swainson, Esq., Attorney General, the following passage occurs:--“Compared with an English summer, that of Auckland is but little warmer, though much longer; but the nights in New Zealand are always cool and refreshing.... The days are _one hour shorter_ in the summer, and _one hour longer_ in the winter than in England! of _twilight_ there is _little_ or _none_.”

From a work, also recently published, on New Zealand, by Arthur S. Thompson, M.D., the following sentences are quoted:--“The summer mornings, even in the warmest parts of the colony are sufficiently fresh to exhilarate without chilling; and the seasons glide imperceptibly into each other. The days are _an hour shorter_ at _each end_ of the day in summer, and an hour longer in winter than in England.”

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.