744 THE POPULAR SCIENCE MONTHLY, 



light. Some Merz telescopes add, from their defects, a purple tint ; 

 and an instrument of another maker gives the spot the color known 

 as Venetian red. Dr. Pigott, who has a With -Browning silvered 

 mirror instrument, and a fine refractor by Wray, finds the latter so 

 unusually well corrected that its performance coincides closely with 

 that of the former. Color-changes, both as regards time and inten- 

 sity, may be caused by the greater or less translucency and refracting 

 powers of the atmosphere through which any object is seen ; but they 

 may also very frequently arise from the greater or less heat and 

 luminosity of solid or viscid matter below the cloudy strata, and 

 from important modifications of chemical action. Between September 

 3d, at from 10.45 to 10.55 p. m., and October 4th, 10.40 p. m., Captain 

 Noble's drawings, made at Maresfield, show a great change in the 

 aspect of the planet, affecting the brightness and the tint of enormous 

 spaces. Parts above the great spot which were brilliant on the former 

 occasion had become cloudy, and, southeast of the spot, there came a 

 round white spot, with very dark surroundings. These changes must 

 have affected many millions of square miles. 



On October 16th, at 10.5 p. m., he noticed the color of the red spot 

 " more marked than ever." There were also extensive changes in the 

 belts, and the polar regions were more cloudy. He made the follow- 

 ing entry in his note-book : " It is a most noticeable feature ; the red 

 spot reposes like an island in the middle of a light space on the plan- 

 et's disk, and the belts, north and south of it, seem in a great measure 

 to conform to its curved outline. This would indicate a disturbance 

 of a stupendous character, from the amount of the area involved." 



On the whole, during the season for observation of 1879-80 Jupi- 

 ter has been more than usually interesting. From pole to pole changes 

 of great magnitude have been produced with prodigality of violence 

 rather than with economy of time. Perhaps the mighty planet is still 

 in the stage of youth, with blazing and explosive energies that a few 

 hundred thousands of years may be required to tame down to the so- 

 berness of our comparatively quiescent earth. — Belgravia. 



[Note. — The red spot spoken of above was watched by an astrono- 

 mer in this country, Mr. E. Leopold Trouvelot, of the observatory at 

 Cambridge, during a part of 1878. He has published an account of his 

 observations in "The Observatory," and ha& furnished to "La Nature" 

 two views of the spot as seen at times three months apart, which we 

 reproduce. In his published description, Mr. Trouvelot says that in 

 looking at Jupiter on September 25, 1878, at six hours and fifty min- 

 utes, he noticed a remarkable red spot a little above the southern bor- 

 der of the equatorial belt, with its center situated a little to the east 

 of the central meridian. It occupied apparently about one fifth of the 

 diameter of the planet, and was quite distinct, its intense rose-color 

 forming a striking contrast with the luminous white ground on which 



