Henry J. Slack

“ At some remote period, when only part of the now solid earth had been condensed from gaseous and vapory matter, our planet might have had a mean density like that of Jupiter, as its rocky materials contain between forty and fifty per cent, of oxygen; and while condensations and chemical combinations were going on rapidly our globe must have been the scene of
"Thunders, lightnings, and prodigious storms." ”

“ With the moon only 240,000 miles off, and very frequently bearing a much higher magnification than can be applied without confusion to Jupiter, telescopes bring no object near. A magnification of 1,000 linear—only usable under very favorable circumstances—makes lunar objects as big, but not as distinct, as a naked-eye vision of them would do if it could approach within 240 miles. With the enormously greater distance of Jupiter it must be evident how impossible it is for anything but huge masses to be seen. ”

“ The softening of the belts, as the planet's rotation brings them to the edges of the disk, probably arises from the dark parts being considerably below the boundary of the Jovian atmosphere, and thus seen through a greater thickness of it when near the edges. When the dark belts touch the edge without noticeable softening they must be higher up, and less likely to be any part of the solid body, if Jupiter has anything that can be so called. The great spot of this season has never been seen close to the edge. ”

“ The planet, though appearing much brighter than any star, gives, according to Mr. Browning, a spectrum fainter than that of a star of the second magnitude. It is the size of the planet and his nearness, as compared with the distance of any fixed star, that make him such a brilliant object. The size of a luminous body greatly affects our estimation of the intensity of its light. Mr. Huggins, at the time mentioned, discovered some dark lines in the Jovian spectrum not belonging to the solar spectrum, and probably resulting from the absorptive action of the planet's atmosphere. ”

“ He made the following entry in his note-book: "It is a most noticeable feature; the red spot reposes like an island in the middle of a light space on the planet's disk, and the belts, north and south of it, seem in a great measure to conform to its curved outline. This would indicate a disturbance of a stupendous character, from the amount of the area involved."
On the whole, during the season for observation of 1879-'80 Jupiter has been more than usually interesting. From pole to pole changes of great magnitude have been produced with prodigality of violence rather than with economy of time. ”

“ Jupiter's diameter is about eleven times that of our earth, and his mean density is about a quarter that of the earth, or about a third more than water. Now, a bulky body may be composed of heavy materials, and still, as a whole, be light, like an iron ship or a lump of pumice-stone, that will float in water. The pumice-lump is light on account of its vesicular formation, so that the mass consists of heavy feldspathic material and the air it contains. ”

“ Jupiter's atmosphere is much larger in proportion to any solid matter he may contain than that of our earth to its solid matter. It is also much denser, and from its greater distance only gets about one twenty-fifth as much solar influence as reaches us. ”

“ Our earth has long been in a state of slow, as distinguished from that of rapid, change. The geologist finds the oldest rocks he can discover affording indications that they were formed when the circumstances of the globe were sufficiently like what they are now for fair comparison. ”

“ Mathematicians tell us that the flattening at the poles noticeable in Jupiter and Saturn, and caused by their rapid rotation, would be greater than measurement shows, if such light bodies were homogeneous. There must, therefore, be some portions much denser than others, and these planets most probably contain matter in all intermediate stages, from the attenuated gaseous, through the viscid, to the solid. ”

“ Most of the earth's crust is formed of solids much heavier than water. Granites are more than two and a half times heavier than water, slaty rocks much about the same, and so are ordinary limestones, the variations of all being from about 2∙5 to 2·9. ”

“ This is curious, as Jupiter has exhibited a good deal of primrose tint, with orange-brown belts and a big orange-brown spot.
A telescopic view of Jupiter usually exhibits some dark belts, occupying a zone of considerable breadth, on either side of the planet's equator, with less conspicuous markings nearer the polar regions. It is also common to find various-shaped patches brighter than the rest. Sometimes the general pattern formed by these markings lasts for months with little visible alteration. At other times a few minutes are sufficient for changes of enormous magnitude. ”

“ A very moderate magnification is sufficient to show that as the planet rotates it comes into view decidedly at some distance from the luminous margin, and disappears at a similar distance from the opposite margin. ”

“ If we assume as probable a modification of the nebular theory, suns and their attendant planets are formed by the condensation of matter in an extreme state of tenuity, and the mass of suns and planets may receive frequent additions in the shape of any smaller or less heavy bodies they are able to attract. ”

“ The "Observatory" for November also quotes the "Chicago Tribune," to the effect that observations at the Dearborn Observatory indicate that changes in the outline of the planet take place from day to day. Two sets of measures at the interval of a week are stated to have shown a difference in the direction of the major axis amounting to 5°.
When extensive belts or bright portions change rapidly, the storm effects must be immensely greater than in any of our hurricanes. Jupiter's motion at the equator is at the rate of about 28,000 miles an hour ”

“ It must often happen, as Chacornac considered traceable in the sun, that condensation produces a great down-rush, and substances that have been solidified falling into hotter regions get melted up or vaporized again. ”