"The lunar halo which by many persons is regarded as a remarkable and unexplained luminosity associated with the moon, is to meteorological students neither a mysterious nor an anomalous occurrence. It has been frequently observed and for many years thoroughly understood, and at the present time admits of an easy scientific explanation. It is an atmospheric exhibition due to the refraction and dispersion of the moon's light through very minute ice crystals floating at great elevations above the earth, and it is explained by the science of meteorology, to which it properly belongs; for it is not of cosmical origin, and in no way pertains to astronomy, as most persons suppose, except as it depends on the moon, whose light passing through the atmosphere, produces the luminous halo, which as will be seen, is simply an optical illusion, originating, not in the vicinity of the moon-two hundred and forty thousand miles away-but just above the earth's surface, and within the aqueous envelope that surrounds it on all sides.... A halo may form round the sun as well as the moon ... but a halo is more frequently noticed round the moon for the reason that we are too much dazzled by the sun's light to distinguish faint colours surrounding its disc, and to see them it is necessary to look through smoked glass, or view the sun by reflection from the surface of still water, by which its brilliancy is very much reduced."...
"A 'corona' is an appearance of faintly coloured rings often seen around the sun and moon when a light fleecy cloud passes over them, and should not be mistaken for a halo, which is much larger and more complicated in its structure. These two phenomena are frequently confounded by inexperienced observers." With these remarks the present writer fully concurs.
Mr. Bartlett adds-
"As a halo is never seen except when the sky is hazy, it indicates that moisture is accumulating in the atmosphere which will form clouds, and usually result in a storm. But the popular notion that the number of bright stars visible within the circle indicates the number of days before the storm will occur, is without any foundation whatever, and the belief is almost too absurd to be refuted. In whatever part of the sky a lunar halo is seen, one or more bright stars are always sure to be noticed inside the luminous ring, and the number visible depends entirely upon the position of the moon. Moreover, when the sky within the circle is examined with even a small telescope, hundreds of stars are visible where only one, or perhaps two or three, are perceived with the naked eye."
It is possible to have five Sundays in February (the year must of course be a "leap year"). This occurred in the year 1880, Sunday falling on February 1, 8, 15, 22, and 29. But this will not happen again till the year 1920. No century year (such as 1900, 2000, etc.) could possibly have five Sundays in February, and the Rev. Richard Campbell, who investigated this matter, finds the following sequence of years in which five Sundays occur in February: 1604, 1632, 1660, 1688, 1728, 1756, 1784, 1824, 1852, 1880, 1920, 1948, 1976.[61]
In an article on "The Last Day and Year of the Century: Remarks on Time Reckoning," in Nature, September 10, 1896, Mr. W. T. Lynn, the eminent astronomer, says, "The late Astronomer Royal, Sir George Airy, once received a letter requesting him to settle a dispute which had arisen in some local debating society, as to which would be the first day of the next century. His reply was, 'A very little consideration will suffice to show that the first day of the twentieth century will be January 1, 1901.' Simple as the matter seems, the fact that it is occasionally brought into question shows that there is some little difficulty connected with it. Probably, however, this is in a great measure due to the circumstance that the actual figures are changed on January 1, 1900, the day preceding being December 31, 1899. A century is a very definite word for an interval respecting which there is no possible room for mistake or difference of opinion. But the date of its ending depends upon that of its beginning. Our double system of backward and forward reckoning leads to a good deal of inconvenience. Our reckoning supposes (what we know was not the case, but as an era the date does equally well) that Christ was born at the end of B.C. 1. At the end of A.D. 1, therefore, one year had elapsed from the event, at the end of A.D. 100, one century, and at the end of 1900, nineteen centuries.... It is clear, then, that the year, as we call it, is an ordinal number, and that 1900 years from the birth of Christ (reckoning as we do from B.C. 1) will not be completed until the end of December 31 in that year, the twentieth century beginning with January 1, 1901, that is (to be exact) at the previous midnight, when the day commences by civil reckoning." With these remarks of Mr. Lynn I fully concur, and, so far as I know, all astronomers agree with him. As the discussion will probably again arise at the end of the twentieth century, I would like to put on record here what the scientific opinion was at the close of the nineteenth century.
Prof. E. Rutherford, the well-known authority on radium, suggests that possibly radium is a source of heat from within the earth. Traces of radium have been detected in many rocks and soils, and even in sea water. Calculation shows that the total amount distributed through the earth's crust is enormously large, although relatively small "compared with the annual output of coal for the world." The amount of radium necessary to compensate for the present loss of heat from the earth "corresponds to only five parts in one hundred million millions per unit mass," and the "observations of Elster and Gertel show that the radio-activity observed in soils corresponds to the presence of about this proportion of radium."[62]
The earth has 12 different motions. These are as follows:-
1. Rotation on its axis, having a period of 24 hours.
2. Revolution round the sun; period 365¼ days.
3. Precession; period of about 25,765 years.
4. Semi-lunar gravitation; period 28 days.
5. Nutation; period 18½ years.
6. Variation in obliquity of the ecliptic; about 47? in 100 years.
7. Variation of eccentricity of orbit.
8. Change of line of apsides; period about 21,000 years.
9. Planetary perturbations.
10. Change of centre of gravity of whole solar system.
11. General motion of solar system in space.
12. Variation of latitude with several degrees of periodicity.[63]
"An amusing story has been told which affords a good illustration of the ignorance and popular notions regarding the tides prevailing even among persons of average intelligence. 'Tell me,' said a man to an eminent living English astronomer not long ago, 'is it still considered probable that the tides are caused by the moon?' The man of science replied that to the best of his belief it was, and then asked in turn whether the inquirer had any serious reason for questioning the relationship. 'Well, I don't know,' was the answer; 'sometimes when there is no moon there seems to be a tide all the same.'"![64]
With reference to the force of gravitation, on the earth and other bodies in the universe, Mr. William B. Taylor has well said, "With each revolving year new demonstrations of its absolute precision and of its universal domination serves only to fill the mind with added wonder and with added confidence in the stability and the supremacy of the power in which has been found no variableness neither shadow of turning, but which-the same yesterday, to-day and for ever-
"Lives through all life, extends through all extent,
Spreads undivided, operates unspent."[65]
With reference to the habitability of other planets, Tennyson has beautifully said-
"Venus near her! smiling downwards at this earthlier earth of ours,
Closer on the sun, perhaps a world of never fading flowers.
Hesper, whom the poets call'd the Bringer home of all good things;
All good things may move in Hesper; perfect people, perfect kings.
Hesper-Venus-were we native to that splendour, or in Mars,
We should see the globe we groan in fairest of their evening stars.
Could we dream of war and carnage, craft and madness, lust and spite,
Roaring London, raving Paris, in that spot of peaceful light?
Might we not in glancing heavenward on a star so silver fair,
Yearn and clasp the hands, and murmur, 'Would to God that we were there!'"
The ancient Greek writer, Diogenes Laertius, states that Anaximander (610-547 B.C.) believed that the earth was a sphere. The Greek words are: µ?s?? te t?? ??? ?e?s?a?, ???t?? t???? ?pe???sa? ??sa? sfa???e?d?.[66]
With reference to the Aurora Borealis, the exact nature of which is not accurately known, "a good story used to be told some years ago of a candidate who, undergoing the torture of a vivâ voce examination, was unable to reply satisfactorily to any of the questions asked. 'Come, sir,' said the examiner, with the air of a man asking the simplest question, 'explain to me the cause of the aurora borealis.' 'Sir,' said the unhappy aspirant for physical honours, 'I could have explained it perfectly yesterday, but nervousness has, I think, made me lose my memory.' 'This is very unfortunate,' said the examiner; 'you are the only man who could have explained this mystery, and you have forgotten...
