第58章 BOOK II.(34)

The outline,shape,and size of this remarkable object has remained without material change from the year 1879,when it was first observed here,until the present time.According to our observations,during the whole of this period it has shown a sharp and well-defined outline,and at no time has it coalesced or been joined to any belt in its proximity,as has been alleged by some observers.During the year 1885the middle of the spot was very much paler in colour than the margins,causing it to appear as an elliptical ring.The ring form has continued up to the present time.While the outline of the spot has remained very constant,the colour has changed materially from year to year.During the past three years (1884-'86)it has at times been very faint,so as barely to be visible.The persistence of this object for so many years leads me to infer that the formerly accepted theory,that the phenomena seen on the surface of the planet are atmospheric,is no longer tenable.The statement so often made in text-books,that in the course of a few days or months the whole aspect of the planet may be changed,is obviously erroneous.The oval white spots on the southern hemisphere of the planet,nine degrees south of the equator,have been systematically observed at every opposition during the past eight years.They are generally found in groups of three or more,but are rather difficult to observe.The rotation period deduced from them is nearly the same as from the great red spot.

These spots usually have a slow drift in longitude of about five seconds daily in the direction of the planet's rotation,when referred to the great red spot;corresponding to a rotation period of twenty seconds less than the latter.'

"This shows,"continued Bearwarden,"that as long ago as towards the close of the nineteenth century the old idea that we saw nothing but the clouds in Jupiter's atmosphere was beginning to change;and also how closely the two English writers and Prof.

Hough were studying the subject,though their views did not entirely agree.A white spot is merely a storm-centre passing round and round the planet,the wind running a little ahead of the surface,which accounts for its rapid rotation compared with the red spot,which is a fixture.A critic may say we have no such winds on earth;to which I reply,that winds on a planet of Jupiter's size,with its rate of rotation--though it is 480,000,000miles from the sun and the internal heat is so near the surface--and with land and water arranged as they are,may and indeed must be very different from those prevailing on earth,the conditions producing and affecting them being so changed.

Though the storm-centre moves two hundred and sixty miles an hour,the wind need not blow at that rate."Later they saw several smaller spots drifting eastward,but concluded that any seaworthy ship might pass safely through them,for,though they were hurricanes of great violence,the waves were small.

"There would be less danger,"said Bearwarden,"of shipping seas here than there is on earth;the principal risk to travellers would be that of being blown from the deck.On account of the air's weight in connection with its velocity,this would necessitate some precaution."The next object of interest was the great red spot.It proved,as Cortlandt had predicted,to be a continent,with at that time no special colour,though they easily recognized it by comparing its outlines with those of the spot in the map.Its length,as they already knew,was twenty-seven thousand miles,and its breadth about eight thousand miles,so that it contained more square miles than the entire surface of the earth,land and water included.

"It is clear,"said Cortlandt,"that at some season of Jupiter's long year a change takes place that affects the colour of the leaves--some drought or prolonged norther;for it is obvious that that is the simplest explanation.In like manner we may expect that at some times more white spots will move across the ocean than at others.""On account of the size of these continents and oceans,"said Bearwarden,"it is easy to believe that many climatic conditions may prevail here that can scarcely exist on earth.But what a magnificent world to develop,with its great rivers,lakes,and mountains showing at even this distance,and what natural resources must be lying there dormant,awaiting our call!This constantly recurs to my mind.The subjugation and thorough opening up of this red spot continent will probably supply more interesting problems than straightening the axis of the earth.""At our next visit,"replied Ayrault,"when we have established regular interplanetary lines of travel,we may have an opportunity to examine it more closely."Then they again attracted the nearest moon beyond which they had swung,increased the repulsion on Jupiter,and soared away towards Saturn.