VIEWS OF JUPITER. 



consequently, been submitted to examination by the most emi- 

 nent observers, and its appearances described with great minute- 

 ness of detail. The apparent diameter in opposition (when it is 

 on the meridian at midnight) is about the fortieth part of that 

 of the moon, and therefore a telescope with the very moderate 

 magnifying power of forty, presents it to the observer with a 

 disc equal to that with which the full moon is seen with the 

 naked eye. 



A power of four or five is sufficient to enable the observer to 

 see the planet with a sensible disc ; a power of thirty shows the 

 more prominent belts ; a power of forty shows it with a disc as 

 large as that which the full moon presents to the naked eye ; 

 but to be enabled to observe the finer streaks which prevail at 

 greater distances from the planet's equator, it is not only necessary 

 to see the planet under favourable circumstances of position and 

 atmosphere, but to be aided by a well-defining telescope with 

 magnifying powers varying from 200 to 300. 



The planet, when thus viewed, appears to exhibit a disc, the 

 ground of which is a light yellowish colour, brightest near its 

 equator, and melting gradually into a leaden-coloured gray 

 towards the poles, still retaining, nevertheless, somewhat of its 

 yellowish hue. Upon this ground are seen a series of brownish- 

 gray streaks, resembling in their form and arrangement the 

 streaks of clouds which are often observed in the sky on a fine 

 calm evening after sunset. The general direction of these streaks 

 is parallel to the equator of the planet, though sometimes a 

 departure from strict parallelism is observable. They are not 

 all equally conspicuous or distinctly defined. Two are generally 

 strikingly observable, north and south of the equator, separated 

 by a bright yellow zone, a part of the general ground of the disc. 

 These principal streaks commonly extend around the globe of 

 the planet, being visible without much change of form during 

 an entire revolution of Jupiter. This, however, is not always 

 the case, for it has happened, though rarely, that one of these 

 streaks, at a certain point, was broken sharply off, so as to 

 present to the observer an extremity so well defined and 

 unvarying for a considerable time as to supply the means of 

 ascertaining, with a very close approximation, the time of the 

 planet's rotation. The borders of these principal streaks are 

 sometimes sharp and even, but, sometimes (those especially 

 which are further from the equator), rugged and uneven, 

 throwing out arms and offshoots. 



On the parts of the disc more remote from the equator, the 

 streaks are much more faint, narrower, and less regular in their 

 parallelism, and can seldom be distinctly seen, except by 



