VIEWS OF JUPITER. 



and when it re-appeared in August, after conjunction, the spots 

 had altogether vanished. 



The observations being continued, the drawings (figs. 5 and 6), 

 were made from observations on the 16th and 17th of January, 

 1836, when the entire aspect of the disc was changed. The two 

 figures (5 and 6) represent opposite hemispheres of the planet. 



It was remarked that the two spots, when carried round by 

 the rotation, became invisible at 55 to 57 from the centre of 

 the disc. This is an effect which would be produced if the 

 spots were openings in the mass of clouds floating in the atmo- 

 sphere of the planet. Their disappearance on moving from the 

 centre of the disc would be caused by their deep sides inter- 

 cepting the view of their bottom, just as we should lose sight of 

 a railway in a deep cutting, if, being placed at the edge of the 

 cutting, we were to withdraw to some distance from it. 



A proper motion with a slow velocity, and in a direction con- 

 trary to the rotation of the planet, was observed to affect the 

 spots, and this motion continued with greater uniformity in March 

 and April, after the disappearance of the belt. 



It was calculated that the velocity of their proper motion over 

 the surface of the planet was at the rate of from three to four 

 miles an hour. 



Although the two black spots were not observed by Madler 

 until the first days of November, they had been previously seen 

 and examined by Schwabe, who observed them to undergo 

 several curious changes, in oue of which one of them disappeared 

 for a certain interval, its place being occupied by a mass of fine 

 dots. It soon, however, re-appeared as before. 



From all these circumstances, and many others developed in 

 the course of his extensive and long-continued observations, 

 Madler considers it highly probable, if not absolutely certain, 

 these vast masses of clouds have a permanence of form, position, 

 and arrangement to which there is nothing analogous in the atmo- 

 sphere of the earth, and that such permanence may in some 

 degree be explained by the great length and very small variation 

 of the seasons. He thinks it probable that the inhabitants of 

 places in latitudes above 40 never behold the firmament at all, 

 and those in lower latitudes only on rare occasions. 



It is also probable that the bright yellowish general ground 

 of Jupiter's disc consists of clouds, which reflect light much more 

 strongly than the most dense masses which are seen illuminated 

 by the sun in our atmosphere ; and that the darker streaks and 

 spots observed upon the disc are portions of the atmosphere, 

 either free from clouds and through which the surface of the 

 planet is visible more or less distinctly, or clouds of less 



