NEWS FROM JUPITER. 
349 
circumstances on which I had been led to base the theory that 
Jupiter is a planet altogether unlike our earth in condition, 
and certainly unfit to be the abode of living creatures. 
I would first direct special attention to the facts which have 
been ascertained respecting the atmosphere of Jupiter. 
It does not appear to have been noticed, as a remarkable 
circumstance, that Jupiter should have an atmosphere recog- 
nisable from our distant station. Yet, in reality, this circum- 
stance is not only most remarkable, but is positively inexplicable 
on any theory by which Jupiter is regarded as a world 
resembling our own. It is certain that, except by the effects 
produced when clouds form and dissipate, our terrestrial 
atmosphere could not be recognised at Jupiter’s distance with 
any telescopic power yet applied. But no one who has studied 
Jupiter with adequate means can for a moment fail to re- 
cognise the fact that the signs of an atmosphere indicate 
much more than the mere formation and dissipation of clouds. 
I speak here after a careful study of the planet during the 
late opposition, with a very fine reflecting telescope by Browning, 
very generously placed at my disposal by Lord Lindsay ; and 
I feel satisfied that no one can study Jupiter for many hours 
{on a single night) without becoming convinced that the cloud- 
masses seen on his disc have a depth comparable with their 
length and breadth. Now the depth of terrestrial cloud-masses 
would at Jupiter’s distance be an absolutely evanescent quantity. 
The span of his disc represents about 84,000 miles, and his satel- 
lites, which look little more than points in ordinary telescopes, are 
all more than 2,000 miles in diameter. I am satisfied that 
anyone who has carefully studied the behaviour of Jupiter’s 
cloud-belts will find it difficult to believe that their depth is 
less than the twentieth part of the diameter of the least 
satellite. Conceive, however, what the depth of an atmosphere 
would be in which cloud-masses a hundred miles deep were 
floating ! 
It may be asked, however, in what sense such an atmosphere 
would be inexplicable, or, at least, irreconcilable with the 
theory that Jupiter is a world like our earth. Such an atmo- 
sphere would be in strict proportion, it might be urged, to the 
giant bulk of the planet, and such relative agreement seems 
more natural than would be a perfect correspondence between 
the depth of the atmosphere on Jupiter and the depth of our 
earth’s atmosphere. 
But it must not be forgotten that the atmosphere of Jupiter 
is attracted by the mass of the planet ; and some rather re- 
markable consequences follow when we pay attention to this 
consideration. Of course a great deal must be assumed in an 
inquiry of the sort. Since, however, we are discussing the 
