Owing to the clear and thin atmosphere of Mars there is very little scintillation of the stars, and the crescent form of the earth at such periods as the present can plainly be discerned without the aid of a gla.s.s. To the Martians this is more readily seen than by us, as their eyes, being larger than ours, have a much greater light grasp.

For the same reason all the stars shine much brighter than they do in our skies, and many of the smaller ones which can be seen from Mars with the unaided eye, would here require a low power-gla.s.s to render them visible to us. The fact that Saturn has a ring is quite apparent to the Martian eye.

Day by day after this we saw the lighted area extending upon the earth, just the same as on the earth Venus can be seen with a telescope gradually to pa.s.s from the crescent phase to the gibbous form, and ultimately become full. Our earth is a morning and evening star to Mars the same as Venus is to the earth, according to its position with regard to the sun.

Whilst we were looking at the earth, I asked Merna "Whether he had ever seen the earth transit the sun as we occasionally see Venus or Mercury do so?"

He answered that "He carefully observed the last transit, which occurred on a date equivalent to our 8th May 1905, and was very interested in watching the earth pa.s.s, as a small black spot, across the sun's disc.

The moon did not commence to cross until 6 hours and 7 minutes later, by which time the earth had pa.s.sed over three-quarters of the sun's diameter. The earth was 8 hours and 42 minutes in transit, and the moon, which crossed a little lower down, was 8 hours and 31 minutes in crossing."

"That must have been an interesting sight," said John, "and I should like to have the opportunity of watching a similar transit."

"I am afraid you never will," said Merna, "for the transits only occur at long intervals. The previous transits occurred in November 1879, November 1800, May 1700, and May 1621. There will not be another until May 1984, and the next after that will not occur until November 2084."

"I am sorry to hear that," remarked John, "for even if I stayed here, I should not be likely to live long enough to see the next transit.

Possibly you may do so, Merna; you are so much younger than I am."

"Yes," Merna replied, "it is not unlikely that I may see another such transit, for the average length of our lives on Mars is about equal to one hundred and thirty of your years, so that leaves me an ample margin of time."

I then went on to remark that as another result of the thinness of the Martian atmosphere twilight is much shorter than on the earth, the light being less diffused when the sun is below the horizon, and refraction also considerably less than we experience.

In this connection, I mentioned to M'Allister that we can often see the sun and the moon apparently above the earth's horizon when they are, in fact, below it. This is caused by the refractive power of our dense atmosphere, which has the effect of making both the sun and the moon appear a little higher up than they really are.

"That is something new to me, Professor," exclaimed M'Allister; "and I cannot say I quite understand how refraction, as you term it, has the effect you mention."

"It may help you, then," I answered, "if I tell you that water acts very much in the same way; and there is a simple and fairly well-known experiment you might try for yourself, which would make the matter perfectly clear to you. It is as follows:--

"Take a teacup and place a shilling at the bottom of it, then move back until you quite lose sight of the coin. Ask some one to pour some clean cold water gently into the cup, and, as it fills, the refraction of the water will apparently reduce the depth of the cup, and thus bring the coin fully into view. In much the same way the refraction of the atmosphere enables us to see the sun or the moon when those bodies are actually below the horizon."

"Thank you, Professor," said M'Allister; "I will try that little experiment at the first opportunity."

I then told him that at the time when the moon is just full it may rise towards the east just as the sun sets towards the west. Both orbs cannot be wholly above the horizon at the same time on such occasions, but, owing to refraction, we are able to see them both.

The sun and moon both appear flattened or oval-shaped just as they are rising or setting, in consequence of the effects of atmospheric refraction. These effects are usually most noticeable near the horizon, because the object is seen through the densest layers of air. But we never see a star in its true place in the sky, because the rays of light which come to us from the star are bent or refracted as they pa.s.s through our atmosphere, just as a stick appears to be bent when thrust down into a deep pool of clear water.

All these effects, however, add to the work of astronomers, because they must be taken into account in connection with their calculations.

As the time pa.s.sed on, I day by day became more interested in Merna's relations with Eleeta.

"All the world loves a lover," and we elderly people are always pleased to note the progress of young folks' love affairs, especially if either of them is a relative of ours. In them we seem to renew our youth, for their entrancements seem to carry us back to the halcyon days when we ourselves were young. When "Love took up the gla.s.s of time and turned it in his glowing hands" everything seemed of a roseate hue, and we dwelt in the seventh heaven of delight, at peace with all the world and envying no one--for were we not the most happy and fortunate of mortals!

And then, to look upon a Martian courtship! To see the rich flushes mount to the cheeks of the lovers--their softly glowing luminous eyes, their absorbed attention in each other, and their mutual deference and response to the most slightly indicated wish! Ah, it was indeed a scene to gladden the heart of the father of one of them!

Eleeta's beauty, the sweetness of her disposition, and most charming and lovable ways endeared her so to me that I did not wonder Merna found them so attractive and satisfying; and my most fervent aspirations ascended for their happiness, both now and in the future.

With the Martians there is no false modesty about their courtships; all is natural, proper, and dignified; every one may see and every one enters into the true spirit of the thing. Mere flirtations, such as we are so familiar with, are quite unknown, as they would be contrary to all the natural instincts of the people. Everything upon Mars is honest, true, and straightforward--open and above-board. This must necessarily be so, in consequence of the Martians' powers of intuition, for any attempt at imposition or deceit would at once be detected.

I had an ill.u.s.tration of this when I asked Merna, "How they dealt with their criminals?"

"We have none to deal with," he replied, "and you will understand why, when I tell you, that if any one committed a crime, however small, and it was desired to find out the offender, it would be impossible to escape detection. He might fly to the other side of our world, but the intuitions of our experts would at once make them aware of his hiding-place; besides, he could not conceal what was on his mind from any one with whom he a.s.sociated.

"In the earlier times when only a small proportion of the Martians were endowed with these powers to any large extent, there were occasional crimes; but as they were always detected, crime soon ceased to exist.

"Thus you will see that, quite apart from their high standard of morality, the Martians soon found that crime was a folly."

There was another love affair apparently developing which did not afford me so much satisfaction as that to which I have just alluded.

I noticed that John and Siloni were very frequently together; and, whatever might be the case with the latter, I had very little doubt that John was smitten with his companion's charms. It was, perhaps, nothing to be wondered at, for Siloni was indeed a very nice girl, with beautiful features, dark hair, and dark eyes; whilst John was well-built, fully six feet in height, with black hair and moustache, and very good-looking; altogether a fine and attractive man, and it had often been a matter of surprise to me that he had never married.

Still, such a complication as this had never entered my mind when I came to Mars, and I was rather perplexed to know how best to deal with the situation. However, I thought it would be well to wait a little while and see how the matter shaped itself before taking any action.

CHAPTER XXII

CELESTIAL PHENOMENA SEEN FROM MARS--M'ALLISTER RECEIVES A PRACTICAL LESSON IN GRAVITATION

Mars is really an ideal world for an astronomer to live in, its skies being so clear, the air so thin and pure, and the stars shining so brilliantly.

Besides these advantages, the rapid movements of the two satellites of the planet result in a constant succession of celestial phenomena which afford very frequent opportunities for most interesting observations.

Changes in the phases of the two moons, eclipses, occultations, transits, &c., are constantly occurring, so there is nearly always something to attract our attention to the Martian sky.

We have already seen several of these phenomena, and I will now describe what we have observed.

Early one evening when we were out with Merna, we looked up at the sky and saw the two moons a considerable distance apart, but approaching each other from opposite directions, Phobos appearing to move very rapidly. Both were near the full phase, Deimos being more nearly full than Phobos; and we watched them drawing closer and closer together till Phobos pa.s.sed right in front of Deimos so as to hide it entirely. This is termed an occultation; and both the satellites had become full when the occultation occurred; but when they were again clear of each other both were beginning to wane.

This sight may be seen anywhere near the Martian equator about every ten hours.

The movements of Phobos seemed very peculiar to us who had lived upon the earth and seen all the celestial bodies appearing to move in the same direction.

I have already alluded to the fact that Phobos is only 3700 miles above the surface of Mars, and moves so rapidly that it makes more than three complete revolutions round the planet whilst the latter is turning only once on its axis.

The effect of this very rapid revolution of the satellite, which has no counterpart, so far as we know, in our Solar system is that, instead of rising in the east and setting in the west as all the other heavenly bodies appear to do, Phobos appears to rise in the west, cross the sky, and set in the east.

The moon and planets all actually move from west to east; the apparent reverse of this being caused by the more rapid movement of the earth on its axis, giving the other bodies the appearance of moving from east to west. If, however, our moon is closely watched, and its position with regard to a fixed star carefully noted, it will be found that in the course of a short time its real movement has been eastward, and that its position with regard to the fixed star has changed, although the revolution of the earth has appeared to carry both westward.

Phobos is 36 miles in diameter. Its actual period of revolution round the planet is 7 hours and 39 minutes, but, owing to the movement of Mars on its axis in the same direction, it appears to take a few minutes over 11 hours to complete one revolution.

Near the equator, Phobos is seen above the horizon for about 4-1/4 hours, and is below it about 6-3/4 hours. According as the place from which it is viewed is farther from the equator so will the time of visibility of Phobos be decreased, until when lat.i.tude 69 is reached in either hemisphere, it will cease to become visible at all. This is owing to its nearness to the planet; and, Mars being small, the curve of its sphere is sharp, so that the horizon is more limited than on the earth, and the satellite is shut out from view anywhere above lat.i.tude 69 by the body of the planet.

Another peculiarity is that, when in the zenith, Phobos appears twice as large in area as it does when near the horizon, and notwithstanding its very small size, Phobos appears rather larger than our moon, because it is so near to the planet.

The length of the Martian "night" is about 12 hours and 20 minutes, and during this very short time Phobos may be seen to rise in the west, set in the east, and rise again once more in the west. Consequently it will be evident that it must travel very rapidly across the sky. It really moves over a s.p.a.ce of 32-1/2 in a single hour--a great contrast to the slow and stately movement of our moon, which only pa.s.ses over half a degree in an hour.