THE PRINCE OF PLANETS.

He made darkness pavilions round about Him, dark waters, and thick clouds of the skies. Through the brightness before Him were coals of fire kindled.-2 SAMUEL Xxii. 12, 13.

ON any evening during the month of April there can be seen, towards the south, a star far brighter than any other in the heavens, except (for a part of the time) the evening star towards the west. The star in the south is the mighty Jupiter, the leader of all the planets, exceeding all the rest together as well in volume as in mass, and so far surpassing our earth in these respects that he may fairly be regarded as a body serving an altogether different purpose in the scheme of creation. I propose to give a brief account of this wonderful globe, pointing out in particular the circumstances which distinguish him from this earth on which we live.

But first let us consider the wonderful contrast between the aspect of this planet as seen by the unaided eye and his real condition as revealed to us by the telescope. Regarding him as he shines on a dark and clear night, we seem to see a bright but small object. Compared with the moon, for instance, Jupiter seems little more than a point of light. Then, watching him from

hour to hour, we observe that he appears to be at rest among the stars, though sharing with them in the motion by which all the orbs of heaven are apparently carried from east to west in consequence of the earth's rotation upon her axis. To the untutored mind Jupiter presents no single feature teaching his real nature and his importance in the creation.

And now, in turn, let us consider what astronomy tells us respecting him.

That small but brilliant orb is a globe so large that, compared with it, our earth is no larger than a pea compared with an orange. Twelve hundred and thirty orbs as large as our earth would be required to form such a globe as Jupiter's. In mass he does not exceed our earth so greatly; but still it would require the mass of three hundred earths to make up Jupiter's. That star which seems to us a point compared with our moon, is attended on by four orbs, the least of which is as large as our moon, while the others are larger than the moon, one being as large as the planet Mercury.

But even more wonderful is the thought of the enormous rate of motion with which that vast orb is being carried along with its attendant family through space. In each second Jupiter's giant bulk moves eight miles, a rate exceeding about five hundred times the velocity of the swiftest express train. I have said that his attendant family is carried along with him. But besides this motion which they share with him, these orbs (which no eye

perceives without telescopic aid, so completely are they lost in the glorious light of their ruling planet) are themselves travelling around Jupiter with motions of enormous rapidity. Nay, the nearest moon travels even faster on its course round Jupiter than Jupiter travels on his course round the sun. It moves no less than eleven miles per second; so that at one part of its course, when its motion conspires with Jupiter's, it is advancing nineteen miles per second, while at the opposite part of its course it is moving backwards at the rate of three miles per second. The other moons have corresponding varieties of motions; and yet these enormous and complex movements are not merely rendered undiscernible by vastness of distance, but the orbs which take part in them are actually invisible until the giant eye of the telescope reveals them to us.

When we know that Jupiter is an orb so mighty, and the centre of a scheme so remarkable, the thought is naturally suggested that he must be the abode of living creatures. It is almost impossible for us to conceive any other purpose for which so noble a planet can have been framed. And let the unbeliever sneer as he will, the thoughtful mind will recognise in such a consideration a valid argument. It is true that men have repeatedly erred when they have attempted to reason from their limited conceptions of the purposes of the Almighty; and it would be incorrect to argue that Jupiter is an inhabited world because the earth is inhabited, and therefore the planets are apparently intended to be inhabited. But if

it could be shown that the only purpose which Jupiter could possibly subserve was that of supplying an abode for living creatures, this would form a very strong argument to most persons, and an irresistible argument to many, in favour of the opinion that Jupiter actually is inhabited.

And yet when we consider the circumstances under which this giant planet exists, we can scarcely suppose that there are living creatures on its surface. There is, in the first place, its enormous distance from the sun, whereby the light and heat received at Jupiter is reduced to less than the twenty-fifth part of that which we receive. It is no doubt true that the actual climate of the planet may depend much on the nature of the Jovian atmosphere; for we see that at the summits of high mountains on the earth, even in tropical regions, a cold so intense prevails that snow perpetually clothes the mountain peaks. But an atmosphere can after all only as it were garner up the heat that it receives; it cannot increase the quantity received. And so far as we know, the only way in which any atmosphere such as we could live in could thus store up the heat received, is by the action of the vapour of water. But it may be doubted whether the sun's direct heat on Jupiter could be capable of causing the water on Jupiter to evaporate to any considerable extent. It is the sun's heat which loads our air with the vapour of water, and then this vapour (especially at night) prevents the heat from escaping so rapidly as it otherwise would. But the

feeble sun of the Jovian sky could hardly raise any water vapour into his atmosphere.

Let us, however, enquire what the telescope tells us about the atmosphere of Jupiter. It is clear that we might expect to find the signs of a great stillness in that atmosphere, if the sun's action alone effected it. For we know that all the disturbances of our own air are due to the sun's heat; wind and cloud, storm and rain, are alike generated by his action. So that where his direct action is so much less as it must needs be in the case of Jupiter, we might expect an unchanging aspect to be presented. But the reality is very different. Examined by a powerful telescope, Jupiter shows all the signs of the most tremendous atmospheric disturbances. There are great bands of clouds all around him, so arranged as to imply the existence of very strong winds resembling our trade winds. But these cloud zones change sometimes so rapidly in shape as to show that either some of the clouds have rapidly discharged their contents in rain and new clouds have been very rapidly formed, or else that great cloud-masses have been carried along with enormous rapidity by winds of hurricane force. In some cases it has been difficult to determine which of these events has taken place, but in others it has been manifest that tremendous storms must have occurred. In passing, indeed, I may remark that it matters very little so far as the main argument is concerned whether we take one view or the other; since it is clear that the formation and dissipation