SOME OF THE ^lARKlttGS ON JUPITER. 5) 



is accomplished in 9 hours 25 minutes, being at the rate 

 of nearly 28,000 miles per hour at its equator, a rapidity 

 sufficiently accounting for the great disparity between its Polar 

 and equatorial diameters, and easily so recognised in a small 

 telescope ; or that its dimensions are about 88*390 miles in mean 

 diameter ; that its apparent mean diameter in arc is 40" "j, 

 varying, of course, according to its distance from the earth, that 

 mean distance being 384,262,000 miles, its mean distance from 

 the sun being 472,693,000 miles. There are many interesting 

 facts connected with these figures which are not intended to be 

 comprised in this paper, which, as intimated, is on the surface 

 markings of the planet. And here we must qualify our title, for 

 it is highly probable some would say certain that we do not 

 see the actual surface of the planet itself, but only the marvellous 

 atmosphere with which the possibly more dense body of the 

 planet is enveloped. It is, therefore, with that atmosphere we 

 have chiefly to deal. It is probably of a semi-fluid or viscous 

 material, and also in a highly-heated condition ; perhaps con- 

 sisting largely of metallic substances at a high temperature not 

 very dissimilar to the sun indeed, in a kindred condition to our 

 own earth when, in long, long past ages, it was cooling down 

 from its nebulous state to a condition susceptible of organic 

 life. 



The spectrum of Jupiter is mainly solar, arising from its 

 reflection of the solar light ; but there are some ill-defined lines 

 not in the sun, and which probably indicate the existence of 

 substances peculiar to the inchoate condition of the planet. Its 

 great distance will suggest the difficulties of this part of Jovian 

 lore, and also the impossibility of organic life, as we know it, on 

 the planet. The physical condition of Jupiter is debateable 

 ground, and will probably ever remain so to us. 



That the different markings of Jupiter lie at varying depths in 

 his atmosphere is a well-ascertained fact, as they have often been 

 seen to pass over each other, and their varying motion and 

 the general manner of their appearance and disappearance give 

 some colouring to the theory that many of them are ejected from 



