250 THE POPULAR SCIENCE MONTHLY. 



to fifty days — from the end of December to the beginning of Febru- 

 ary. Among these, sixteen evenings were remarkably favorable, so 

 much so that the greatest magnifying powers could be used. 



It was therefore possible, notwithstanding the fact that the ap- 

 parent diameter of Mars was not over 16* (against 19" in 1877), to 

 obtain results which surpass all previous endeavors. Beginning with 

 the white polar spots, Schiaparelli first mentions that the northern 

 polar spot was always more or less visible. During the months of 

 November and December it appeared separated into several branches 

 or masses, as was also the case in 1879. In the latter half of January 

 these branches began to amalgamate and form a regular, continuous, 

 and uniform calotte, the diameter of which reached about 50° at the 

 beginning of February, and then decreased in a distinctly noticeable 

 manner ; while, on the contrary, the southern polar spot remained 

 invisible during the entire period of the observations, even in January 

 and February, when the south pole entered the field of view 2°. From 

 this, in connection with the experience gained in 1879 relative to the 

 visibility of the spot, he concludes that eight months after the southern 

 solstice it had not yet attained a diameter of 20° — a diameter which, 

 according to the observations during the previous opposition, it gen- 

 erally attained to a few weeks before this solstice. 



During the course of the observations, various white or whitish 

 spots made their appearance at the southern edge of the planet, greatly 

 resembling the polar spot, but after exact examination and measure- 

 ment proved to be one or the other of the well-known southern islands 

 of the planet, which appeared white around their edges in considera- 

 tion of a property peculiar to these localities. 



The dark portion (ocean ?) which surrounds these islands did not 

 seem to possess this property ; and, in order to explain how the polar 

 spot, during the southern winter on Mars, can occupy a part of this 

 locality, it becomes necessary to make the assumption that at such 

 times this part undergoes such changes that it is enabled to appear of 

 a bright white color. 



Similar white or whitish spots were observed at intervals at other 

 points of the yellow surface of the planet ; some of the better deter- 

 mined points, which had already been noticed in 1877 and 1879, were 

 also visible on this occasion, while others remained invisible. A num- 

 ber of white spots were observed, which, however, were only tempo- 

 rary, particularly in the neighborhood of the northern polar calotte. 

 Emanating from this position, there often would be noticed white in- 

 clined stripes passing toward the equator of the planet ; the arrange- 

 ment of these seemed to be dependent upon the rotation of Mars — 

 other positions near the edge of the planet likewise presented a whitish 

 appearance. 



A general dimming of the white spots which hid the configura- 

 tion of the planet was observed on the 18th of January, between 



