236 Original Articles. [April, 



that beneath them must be much denser ; still, the whole much deeper 

 than ours. The effect of such an arrangement in elevating the general 

 temperature has been already pointed out. The position, form, and 

 movements of the planet's clouds were admirably seen by Prof. C. P. 

 Smyth, under the fine atmospheric conditions afforded by an elevation 

 of 11,000 ft. on the Peak of Teneriffe. " There," he remarks, " the mere 

 streaky bands which cross his disc become resolved in the telescope 

 under high powers into regions of cloud. The brighter spaces were 

 the clouds, and their forms were as characteristically marked and were 

 drifting along as evidently under the influence of a rotation wind as 

 the cumuli and cumulo-strati, which the terrestrial N.E. current was 

 at that moment bringing past Teneriffe under our feet — while in addi- 

 tion there were minute changes in the relative positions and forms of 

 the vaporous masses in either hemisphere, indicating as well the pre- 

 sence of wind as the ephemeral nature of mist. Far more striking, 

 however, was the testimony borne by the more constant form of the 

 clouds seen best towards the equatorial parts of the planets. At this 

 tract one could not gaze long without acquiring the impression of 

 looking at a windy sky ; the whole zone of vapour seemed to be in 

 motion, while from its ragged edge portions were torn off and were 

 driving along, some of them rolling over and over, and others pulled 

 out in length." 



A better description of a clouded terrestrial sky could scarcely be 

 given. One very suggestive feature was noticed clearly by Prof. 

 Smyth, namely, that the comparative calmness in the equatorial re- 

 gion which has been so often observed, and which as he remarked 

 seemed more inclined to strati and cirro-strati than to the tempestuous 

 cumuli of the tropics, was not exactly coincident with the equator. 

 This is also evident in the beautiful drawing of Jupiter, by Mr. 

 De la Eue, which forms one of the illustrations to this paper, and 

 "seems to require the operation of some such cause as makes the 

 southern trades overbalance the northern ones on the Earth, and 

 throw the zone of equatorial calm into northern latitudes, namely, the 

 unequal distribution of land and sea surface in the two hemispheres." 

 Besides the appearances above described, which are the ordinary ones, 

 there are others at times indicating greater periodical changes, such 

 as large black tracts, numerous glistening spots, &c. 



In the conditions of Jupiter thus far ascertained, in many respects 

 so analogous to those which prevail on the Earth, none appear which 

 are inimical to life — none, indeed, wider than are known to embrace 

 it within their limits. The increased weight of bodies on his surface, 

 owing to his greater attraction, when subjected to the reductions due 

 to his larger radius, less specific gravity, and increased centrifugal 

 force (which last is sixty-three times as great as the Earth's), would be 

 less than two-and-a-half times what it is on our planet, a difference 

 scarcely without parallel in cases of living animals possessing nearly 

 equal muscular power. 



The very small angle of 1° 18' 52" which the planet's orbit makes 

 with the ecliptic, combines with his dense and vaporous atmosphere to 

 produce a considerable equality of climate on all parts of the surface. 



