740 THE POPULAR SCIENCE MONTHLY. 



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 con- 

 densations and chemical combinations were going on rapidly our globe 

 must have been the scene of 



"Thunders, lightnings, and prodigious storms." 



And it is probable that certain stars which have suddenly blazed forth 

 with passing splendor have exhibited to us the spectacle of conflagra- 

 tions extending over millions and billions of square miles. Color- 

 changes in Jupiter — such as those noticed by Mr. Browning and the 

 writer in 1869-'70 — may have been caused by soda-flames, though not 

 fierce enough or extensive enough to add materially to his ordinary 

 luminosity, which is estimated as always exceeding, though not in a 

 very high degree, what it would be by mere reflection of light received 

 from the sun. A drawing after Mr. Browning was published in the 

 fifth volume of the " Student and Intellectual Observer," showing a 

 broad, full, yellow equatorial belt ; also broad belts of pui-plish brown 

 edged with narrower yellow bands above and below it, and curious 

 white patches in the upper dark belt. The polar belts were purplish 

 and olive. The appearance and disappearance of these remarkable 

 belts indicated great physical changes, and it is to be regretted that 

 spectroscopes could not afford so much information as was hoped fpr. 

 The planet, though appearing much brighter than any star, gives, ac- 

 cording 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 esti- 

 mation of the intensity of its light. Mr. Huggins, at the time men- 

 tioned, discovered some dark lines in the Jovian spectrum not belong- 

 ing to the solar spectrum, and probably resulting from the absorptive 

 action of the planet's atmosphere. He also pointed out that the re- 

 markable yellow color had been seen some years before. Quite recently 

 Mr. Huggins has been employing his large reflector to take photo- 

 graphic spectra of the planet, and he informs the writer that " from G 

 to O in the outer violet there is no sensible modification, either in ad- 

 dition or absence of lines, of the solar spectrum." 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 plan- 

 et'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 min- 



