is a London on Venus the Londoners there must be of singularly strong constitutions. It is thought a trying change for the ordinary Londoner to visit the hotter regions of the tropical zone; and it is an even more trying change for him to penetrate within the Arctic regions. But to have a summer more than twice as hot as our hottest torrid weather, a cold as extreme as that of our Arctic winters, succeeding each other at intervals of four months, would certainly kill in a year or two not merely the ordinary Londoner, but the hardiest specimen of the hardiest races of mankind. But assuredly "Touching the Almighty we cannot find Him out; He is excellent in power and in judgment, and in plenteousness of justice; He will not afflict.' THE RUDDY PLANET. The snows that glittered on the disc of Mars Rolls in the crimson summer of its year.-HOLMES. DURING May there shines in the south a ruddy orb which can scarcely be mistaken for a fixed star. It is the planet Mars pursuing his course (now retrograde) through the constellation of the Virgin. In this constellation there is but one star which is comparable in brilliancy with the planet Mars-the star Spica Azimech, which marks the ear of corn carried in the maiden's hand; and the eye recognises at once a marked difference between the sparkling light of the star and the steady glow of the ruddy planet. It may in passing be noticed that a fine opportunity is afforded the young astronomer of observing the chief distinction between a planet and a fixed star. It is quite commonly imagined that only long and patient watching can reveal the movements which are characteristic of the planets (and whence, indeed, they derive their name, since the word planet signifies a wanderer'). But even in a few hours Mars perceptibly changes his place among the fixed stars; and if he be watched night after night during a favourable opportunity— let us say from the end of May until the end of June —he will be seen to traverse a very considerable portion of one of the great loops in which he circuits the zodiac. I can imagine few more instructive or suggestive exercises than thus to track a planet which, like Mars, or Jupiter, or Saturn, is conspicuous from time to time in our night skies as distinguished from the twilight skies on which the planet Venus pursues her course. The task is not at all a difficult one. All that is necessary is to prick down on a sheet of white paper the stars of the constellation which the planet is traversing. The ordinary almanacs tell us which constellation this chances to be, and any good star-atlas will give the conspicuous stars. Then each night the young astronomer should notice where the planet is situated among these stars, and should jot down its place accordingly in his star-sheet. When a few days have passed he will begin to recognise the nature of the track which the planet is pursuing, and he will have pursued himself a portion of the track by which the earliest astronomers were gradually led to the knowledge of the true arrangement of that wonderful scheme of orbs over which the sun bears sway. Nay, if the planet he has selected has been Mars-now the best placed by far for the purpose, and always remarkable when so placed for the rapidity of his motions-the young astronomer will have been repeating, in a rough way, the observations which led Kepler to the knowledge of those laws on which Newton based the whole system of modern astronomy. It appears to me that the study of the heavens is not less instructive in this aspect than in the wonderful facts which it has. revealed. I find, indeed, a special charm in the contemplation of the great problems of astronomy as they presented themselves to men before the time had come when the great secret of the universe was to be revealed. There is much in the thoughts suggested by such contemplation to afford encouragement on the one hand, and to teach modesty on the other. If we feel gratification, and some degree of pride in the intellectual powers given to man, when we consider the marvellous way in which the truth in these matters has been attained, we must nevertheless perceive how prone man is to error, when we recall how for century after century a false system of astronomy was complacently taught at all the great seats of learning. There is another excellent reason for studying the actual motions of the celestial bodies when favourable opportunity occurs. This reason is that set forth by Milton, when he makes the archangel say to Adam :- To ask or search I blame thee not; for Heaven His seasons, hours or days or months or years. And no other subject of observation is pleasanter or more instructive than the movement of the planets, as they pursue Their wand'ring course,-now high, now low, then hid, Let us pass, however, to the consideration of the planet Mars as exhibited to us by the teachings of astronomy. We note, then, first, that Mars is strikingly contrasted to the two planets hitherto considered-Venus and Jupiter ---unlike though these two planets are to each other. 'One star differeth from another star in glory.' We may, indeed, almost say that in the whole heavens there are not two orbs which resemble each other. In considering Venus we were struck by the great amount of light and heat which she receives from the sun. With Mars all this is reversed. For whereas Venus is the planet which travels next to the earth on the inside, or towards the sun, Mars travels next to the earth on the outside, or away from the sun. Accordingly he receives much less light and heat than the earth; his actual supply (considering mile per mile of surface) varies from one-half to one-third of the earth's supply, this great variation being due to the eccentric nature of the path on which he travels. Thus, while Venus receives twice as much light and heat as the earth, Mars never receives more than half as much as the earth, or one-fourth of the supply afforded to Venus. Mars also differs remarkably from Venus and our earth in size, and it is in this respect that he affords |