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fairly rapid motion of its own, as it moved eastward across the

surface of the ocean. It exhibited all the phenomena of the

storm they had watched in crossing Secretary Deepwaters Bay, but

covered a larger area, and was far more violent. Their glasses

showed them vast sheets of spray driven along at tremendous

speed, while the surface was milky white.

"This," said Bearwarden, picking up a book, "solves to my mind

the mystery of the white spot described by the English writer

Chambers, in 1889, as follows:

"'During the last few years a brilliant white spot has been

visible on the equatorial border of the great southern belt. A

curious fact in connection with this spot is, that it moves with

a velocity of some two hundred and sixty miles per hour greater

than the red spot. Denning obtained one hundred and sixty-nine

observations of this bright marking during the years 1880-1883,

and determined the period as nine hours, fifty minutes, eight and

seven tenths seconds (five and a half minutes less than that of

the red spot). Although the latter is now somewhat faint, the

white spot gives promise of remaining visible for many years.

During the year 1886 a large number of observations of Jupiter

were made at the Dearborn Observatory, Chicago, U. S., by Prof.

G. W. Hough, using the eighteen-and-a-half-inch refractor of the

observatory. Inasmuch as these observations are not only of high

intrinsic interest, but are in conflict, to some extent, with

previous records, a somewhat full abstract of them will be

useful: The object of general interest was the great red spot.

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 1885 the 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

480,000,000 miles 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.

"We have a striking illustration of Jupiter's enormous mass,"

said Cortlandt, as the apparent diameter of the mighty planet

rapidly decreased, "in the fact that notwithstanding its numerous

moons, it still rotates so rapidly. We know that the earth's

days were formerly but half or a quarter as long as now, having

lasted but six or eight hours. The explanation of the elongation

is simple: the earth rotates in about twenty-four hours, while

the moon encircles it but once in nearly twenty- eight days, so

that our satellite is continually drawing the oceans backward

against its motion. These tidal brakes acting through the

friction of the water on the bottom, its unequal pressure, and

the impact of the waves on the shore, are continually retarding

its rotation, so that the day is a fraction of a second longer

now than it was in the time of Caesar. This same action is of

course taking place in Jupiter and the great planets, in this

case there being five moons at work. Our moon, we know, rotates

on its axis but once while it revolves about the earth, this

being no doubt due to its own comparative smallness and the great

attraction of the earth, which must have produced tremendous

tides before the lunar oceans disappeared from its surface."

In crossing the orbits of the satellites, they passed near

Ganymede, Jupiter's largest moon.

"This," said Cortlandt, "was discovered by Galileo in

1610. It is three thousand four hundred and eighty miles

in diameter, while our moon is but two thousand one

hundred and sixty, revolves at a distance of six hundred

and seventy-eight thousand three hundred miles from

Jupiter, completes its revolution in seven days and four

hours, and has a specific gravity of 1.87."

In passing, they observed that Ganymede possessed an atmosphere,

and continents and oceans of large area.

"Here," said Bearwarden, "we have a body with a diameter about

five hundred miles greater than the planet Mercury. Its size,

light specific gravity, atmosphere, and oceans seem to indicate

that it is less advanced than that planet, yet you think Jupiter

has had a longer separate existence than the planets nearer the

sun?"

"Undoubtedly," said Cortlandt. "Jupiter was condensed while in

the solar-system nebula, and began its individual existence and

its evolutionary career long before Mercury was formed. The

matter now in Ganymede, however, doubtless remained part of the

Jupiter-system nebula till after Mercury's creation, and, being

part of so great a mass, did not cool very rapidly. I should say

that this satellite has about the same relation to Jupiter that

Jupiter has to the sun, and is therefore younger in point of time

as well as of development than the most distant Callisto, and

older, at all events in years, than Europa and Io, both of which

are nearer. This supposition is corroborated by the fact that

Europa, the smallest of these four, is also the densest, having a

specific gravity of 2.14, its smallness having enabled it to

overtake Ganymede in development, notwithstanding the latter's

start. In the face of the evidence before us we must believe

this, or else that, perhaps, as in the case of the asteroid

Hilda, something like a collision has rejuvenated it. This might

account for its size, and for the Nautical Almanac's statement

that there is a 'small and variable' inclination to its orbit,

while Io and Europa revolve exactly in the plane of Jupiter's

equator."

They had about as long a journey before them as they had already

made in going from the earth to Jupiter. The great planet soon

appeared as a huge crescent, since it was between them and the

sun; its moons became as fifth- and sixth-magnitude stars, and in

the evening of the next day Jupiter's disk became invisible to

the unaided eye. Since there were no way stations, in the shape

of planets or asteroids, between Jupiter and Saturn, they kept

the maximum repulsion on Jupiter as long as possible, and moved

at tremendous speed. Saturn was somewhat in advance of Jupiter

in its orbit, so that their course from the earth had been along

two sides of a triangle with an obtuse angle between. During the

next four terrestrial days they sighted several small comets, but

spent most of their time writing out their Jovian experiences.

During the sixth day Saturn's rings, although not as much tilted

as they would be later in the planet's season, presented a most

superb sight, while they spun in the sun's rays. Soon after this

the eight moons became visible, and, while slightly reducing the

Callisto's speed, they crossed the orbits of Iapetus, Hyperion,

and Titan, when they knew they were but seven hundred and fifty

thousand miles from Saturn.

"I am anxious to ascertain," said Cortlandt, "whether the

composition of yonder rings is similar to that of the comet

through which we passed. I am sure they shine with more than

reflected light."

"We have been in the habit," said Ayrault, "of associating heat

with light, but it is obvious there is something far more subtle

about cometary light and that of Saturn's rings, both of which

seem to have their birth in the intense cold of interplanetary

space."

Passing close to Mimas, Saturn's nearest moon, they supplemented

its attraction, after swinging by, by their own strong pull,

bringing their speed down to dead slow as they entered the

outside ring. At distances often of half a mile they found

meteoric masses, sometimes lumps the size of a house, often no

larger than apples, while small particles like grains of sand

moved between them. There were two motions. The ring revolved

about Saturn, and the particles vibrated among themselves,

evidently kept apart by a mutual repulsion, which seemed both to

increase and decrease faster than gravitation; for on approaching

one another they were more strongly repelled than attracted, but

when they separated the repulsion decreased faster than the

attraction, so that after a time divergence ceased, and they

remained at fixed distances.

The Callisto soon became imbued with motion also, but nothing

ever struck it. When any large mass came unusually near, both it

and their car emitted light, and they rapidly separated. The

sunlight was not as strong here as it had been when they entered

the comet, and as they penetrated farther they were better able

to observe the omnipresent luminosity. They were somewhat

puzzled by the approach of certain light-centres, which seemed to

contain nothing but this concentrated brightness. Occasionally

one of these centres would glow very brightly near them, and

simultaneously recede. At such times the Callisto also glowed,

and itself recoiled slightly. At first the travellers could not

account for this, but finally they concluded that the centres

must be meteoric masses consisting entirely of gases, possessing

weight though invisible.

"We have again to face," said Cortlandt, "that singular law that

till recently we did not suppose existed on earth. All kinds of

suppositions have been advanced in explanation of these rings.

Some writers have their thickness, looked at from the thin edge,