DISCOVERY 



63 



was made by Nasmyth in 1853. But it was not until 

 1865 that the evidence adduced by Zollner, of Leipzig, 

 convinced the contemporary astronomers that Jupiter 

 was no enlarged edition of our own world, but was, 

 indeed, a semi-sun. Zollner drew attention to the 

 rapid changes in the cloud-belts both of Jupiter and 

 Saturn. Such changes, he showed, indicated clearly a 

 liigh internal temperature for both planets, for the 

 heat of the Sun at the distance of Jupiter is quite in- 

 capable of causing atmospheric disturbances on so vast 

 a scale. Zollner drew attention, too, to another analogy 

 between Jupiter and the Sun, namely that the planet, 

 as Herschel had noted long before, does not rotate 

 as a whole, but that the rotation is accelerated in the 

 equatorial regions. Clearly this fact conflicted directly 

 with the current theory of the planet's physical con- 

 dition. The new view of Jupiter and of the giant 

 planets in general was adopted by the late R. A. Proctor 

 early in his career, and presented with convincing logic 

 in 1870 in his classic volume. Other Worlds than Ours. 

 " If analogy is to be our guide," he WTote, " and we 

 are to judge of the condition of Jupiter according to 

 what we know or guess of the past condition of the 

 Earth and the present condition of the Sun, we seem 

 led to the conclusion that Jupiter is still a glowing 

 mass, fluid probably throughout, still bubbling and 

 seething with the intensity of the primeval fires, 

 sending up continually enormous masses of cloud to 

 be gathered into bands under the influence of the swift 

 rotation of the giant planet." The conception of 

 Jupiter as a body, half sun, half world, has never since 

 been challenged. 



In the seventies a new period in the study of Jupiter 



was inaugurated, which may be called the period of 



intensive observation. The discovery by Niesten 



at Brussels, in July 1878, of the remarkable object 



known as the " great red spot " gave an impetus to 



much more detailed study of the spots — both bright and 



dark — and the more delicate detail on the Jovian disc. 



Eminent observers such as Keeler, Lowell, and Barnard 



have kept the planet under observation with the aid 



of the most powerful telescopes ; and in addition a 



great deal of important information has been collected 



by several non-professional astronomers, among whom 



must be specially mentioned Messrs. Denning, Stanley 



Williams, Phillips, Molesworth, and Bolton. Denning's 



patient study of the great red spot has shown that it 



was probably visible long before 1878 ; he believes it 



to have been seen by Schwabe in 183 1, and probably 



by Hooke in 1664. The long-continued work of Mr. 



Stanley Williams indicated to that astronomer in 



1896 the existence of nine different currents in the 



Jovian atmosphere, made manifest by the different 



rotation-periods obtained from observations of spots 



in the various latitudes. In 1901 Molesworth, observ- 



ing in Ceylon, was the first to catch a glimpse of the 

 beginnings of the "southern tropical disturbance," 

 which has been conspicuous on the disc for the past 

 twenty years. Another significant discovery, due to 

 Mr. Scriven Bolton, was abundantly confirmed by 

 Professor Lowell at the Lowell Observatory. Mr. 

 Bolton detected " wisps " or " lacings " extending 

 across the bright equatorial belt, and Lowell pointed 

 out that these strips are not confined to the equatorial 

 belt, but are to be seen traversing all the bright belts 

 right up to the poles. 



Several attempts have been made in recent years to 

 correlate in a general theory of the planet's constitu- 

 tion all the isolated facts which have been ascertained 

 during the past half-century. The late Danish astro- 



JVriTliR, FEBRUARY 17. igo'J- 

 From a drauiug by Ihe Rev- James Baiku; Edinburgh. 



nomer, H. E. Lau, of Copenhagen, put forward shortly 

 before his premature death a theory of the planet 

 based on his own observations. The true surface of 

 the planet, he maintained, consists of a bright yellow 

 cloud envelope, highly reflective, enveloped in a much 

 thinner atmospheric stratum. The equatorial zones 

 he believed to be spot-zones, the behs consisting of dark 

 spots. " The bright spots are apparently clouds over- 

 lying the hottest places. Their brightness varies with 

 the sun-spot activity, so that a periodic change of bright- 

 ness in the planet is produced. The red spot is an abnor- 

 mally heated region in the deeper strata of the gaseous 

 envelope." This does not conflict with Lowell's view 

 that the red spot is due to " a vast uprush of heated 

 vapour from the interior ... a sort of baby elephant of 

 a volcano, or geyser, occurring as befits its youth m 

 fluid, not solid conditions, but fairly permanent 

 nevertheless— a bit of kindergarten Jovian geology." 



