178 



KNOWLEDGE, 



[August, 1903. 



of this gigantic orb will ever be exhausted ; the variations 

 ia his markings, both as regards their aspect and velocity, 

 are so diversified and the objects so abundant that they 

 offer a comparatively boundless field for investigation. 

 There is indeed every reason to suppose that the ensuing 

 few years will witness increased enthusiasm among Jovian 

 students in the northern hemisphere, to whom the planet 

 wiU attain a much greater altitude, and appear under a 

 better defined aspect than during the past few oppositions. 

 As now displayed in the morning sky, Jupiter exhibits 

 many prominent and curious markings. It is true that no 



in surveying this planet is to obtain as many accurate 

 estimates as possible of the times when the various spots 

 pass tile central meridian, as these materials enable the 

 individual rates of velocity to be ascertained. The lielts 

 and zones of Jupiter may be likened to a series of parallel 

 rivers running along at different speeds, and the irregular 

 spots floating in them afford just the clues re(juired to 

 enable us to ascertain the relative strength of the currents. 

 The study of Jovian detail is essentially directed to questions 

 of motion rather than of aspect, and in its aims and issues 

 is very dissimilar to telescopic enquiries concerning liars, 



LoNGiTunEs OF THE Equatoei.al Spots (White O. Dark %) on Jupiteb, 1902. 



/fl>2. 



•^^^>i^4n^4a^^^iHnm^TII>||^^Tl||^^.7--^'f;>l,^a.^^i.^'^ 



Observations with a 10-inch Eeflectob, power 312, by W. F. Denning, Bristol. 



distinctly sensational feature happens to be visible, such as 

 the slant-belt of 1860, the great red spot in its striking 

 tint and bold outline of 1878-80, or the rapidly-moving 

 north-temperate spots of 1880 and 18!>1. But there are a 

 large number of objects perceptible which it is desirable to 

 watch as closely as possible during the remaining part of 

 the opposition. Observers who have micrometers would 

 do well to determine the latitudes of the principal belts 

 and spots eveiy year. Perhaps, however, the main object 



which have special i-eference to the forms and positions of 

 tlie Lineaments. This is due to the fact that the spots on 

 Mars are actual surface formations, one and all influenced 

 by an invariable rotation period of 24h. 37in. 22'62s. But 

 telescopic observers of Jupiter are merely studying the 

 outside meteorology of the planet, since his vaporous 

 envelopes preclude any closer acquaintance with the 

 phenomena of his real globe. 



We may never be able to penetrate this obstructive veil 



