to avoid, above all things, any attempt to inquire what may be the true meaning of observations already made, and to ask constantly for more observations.
Now, however, we receive news of an observation which sets the question finally at rest. When one of Jupiter's moons passes behind the body of the planet, the moon does not necessarily enter the planet's shadow. It only does so when the sun, the earth, and Jupiter are nearly in a straight line; when the earth is considerably removed from the line joining Jupiter and the sun, a satellite passing behind the planet's outline on one side remains in sunlight for a considerable time. It probably has not occurred to any observer to try to see a satellite when thus in sunlight behind the planet. On the old theory, of course, it would have been absurd to look for a satellite under such conditions, when there would be several thousand miles of the planet's solid substance in the way. But of course, if the planet has an atmosphere thousands of miles deep, laden more or less heavily with cloud-masses, it might quite readily happen that a satellite should be seen apparently through the planet,—not, of course, through the middle of the planet, but through parts lying thousands of miles within the apparent outline. This is what has now actually happened. We should not quote the observation, if it were not, in the first place, one which will probably be repeated (now that it has once been made), and if it had not, in the second place, been accepted by astronomers. It is thus recorded by the council of the Astronomical Society. "A very interesting phenomenon was observed more than once independently by Mr. Todd, of Adelaide, using a new eight-inch telescope by Cooke, and his assistant, Mr. Ringwood, when a satellite was on the point of being hidden. Instead of disappearing gradually behind the planet, it was apparently projected on the disc, as if viewed through the edge of the planet, supposing the latter were surrounded by a transparent atmosphere laden with clouds. This curious phenomenon was noticed on two occasions at the disappearance of the first satellite, when it was thus distinctly visible through the edge of the disc for about two minutes before it was finally concealed." It must, therefore, have been seen where the line of sight passed fully two thousand miles below the apparent outline of the planet, or along a range of fully twelve thousand miles of cloud-laden air. It may safely be inferred from this observation that the planet has an atmosphere extending six or seven, probably ten or twelve thousand miles below the apparent outline, so that a globe as large as our earth lying on. the surface of Jupiter might not reach, or only barely reach, his outermost cloud-layers.
This is one of the most interesting discoveries yet effected by direct astronomical observation. It had indeed been inferred by a few astronomers, careful to interpret results already obtained, that Jupiter must be in the condition which the Australian observation indicates. But at present, and probably for many years yet to come, theories based on mere reasoning, however conclusive in reality, must be "caviare to the general," and we must still be content to wait (as recently in the case of the solar corona) till observations which every one can understand have demonstrated what only the few could infer confidently from reasoning based on less simple observations.
From St. James's Magazine.
MAIL COACHES.
The letters, Mr. Palmer proposed, should be carried in strong and well-guarded coaches made expressly for the purpose, while the post-horses should be the finest England could supply; each coach should be accompanied by a man carrying firearms, and the post-boys should be well equipped for any dangers they might encounter: the coaches laden with the London mails were all to start from London at the same hour every evening, and their departure from the country should be so regulated as to ensure as far as possible their simultaneous arrival in London every morning. This plan, admirably as it was in harmony with the English taste, even to every exact detail, and hailed as it was, accordingly, with cheers from the multitude, met with opposition from a large and powerful party, and angry discussions arose in the wayside inns, at the clubs, at the dining-table, in the drawing-room, and even in the streets; for there were in those days, as now, many who set themselves resolutely to oppose any novelty, as fraught with evils, and dangers innumerable. . . . William Pitt, with his usual sagacity, at once comprehended that it was both excellent and practicable: accordingly the country was, after a few more exclamations from the malcontents, brought to the decision that Mr. Palmer's mail-coach
