NEWS FROM JUPITEK. 
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planet’s disc, must have been reflected sunlight. In fact, from 
what we know about the actual quantity of light received from 
Jupiter, we may be quite certain that no very large portion of 
that light is inherent. Jupiter shines about as brightly as 
if he were a giant cumulus-cloud, and therefore almost as white 
as driven snow. Thus he sends us much more light than a 
globe of equal size of sandstone, or granite, or any known kind 
of earth. We get from him about three times as much light 
as a globe like our moon in substance, but as large as Jupiter, 
and placed where Jupiter is, would reflect towards the earth ; 
but not quite so much as we should receive from a globe of 
pure snow of the same size and similarly placed. It is only 
because large parts of the surface of Jupiter are manifestly not 
white, that we seem compelled to assume that some portion of 
his light is inherent. 
But the theory that Jupiter is intensely hot by no means 
requires, as some mistakenly imagine, that he should give out 
a large proportion of light. His real solid or liquid globe (if 
he have any) might, for instance, be at a white heat, and yet 
so completely cloud-enwrapped that none of its light could 
reach us. Or, again, his real surface might be like red-hot 
iron, giving out much heat but very little light. 
I shall close the present statement of evidence in favour of 
what I begin to regard as in effect a demonstrated theory, with 
the account of certain appearances which have been presented 
by Jupiter’s fourth satellite during recent transits across the 
face of the planet. The appearances referred to have been 
observed by several telescopists, but I will select an account 
given in the monthly notices of the “ Astronomical Society,” 
by Mr. Koberts, F.E.A.S., who observed the planet with a fine 
telescope by Wray, 8 inches in aperture. “ On March 26, 
1873,” he says, ‘‘I observed Jupiter about 8 p.m., and found 
the fourth satellite on the disc. I thought at first it must be 
a shadow ; but, on referring to the ‘ Nautical Almanac,’ found 
that it was the fourth satellite itself. A friend was observing 
with me, and we both agreed that it was a very intense black, 
and also was not quite round. We each made independent 
drawings which agreed perfectly, and consider that the obser- 
vation was a perfectly reliable one. We could not imagine 
that such an intensely black object would be visible when off 
the disc, and waited with some impatience to see the emersion, 
but were disappointed by fog, which came on just at the 
critical time.” Another observer, using a telescope only two 
inches in aperture, saw the satellite when off the disc, so that 
manifestly the blackness was merely an effect of contrast. 
In considering this remarkable phenomenon, we must not 
forget that the other satellites do not look black (tliough some 
