SURFACE CHARACTERS OF THE PLANET MARS. 251 



the meridians of 40 and 120. It extended only over the yellow- 

 portions, which are supposed to be continents, and often covered the 

 canals, but completely avoided the darker portions, which represent 

 the oceans and larger lakes. It was not a contiguous covering, but 

 consisting of white or whitish spots, which were irregularly distrib- 

 uted. 



The atmosphere of Mars appears to have been more transparent 

 than during 1877. Not only the luminous and the opaque zone of the 

 rim were smaller, but in some parts of the planet the contrast between 

 the light and shade was more distinctly visible with an inclined illu- 

 mination, and so it w^as possible to more readily distinguish objects 

 at the edge of the planet than at the center. 



During November the north pole advanced some 7 to 8 within 

 the circle of the visible hemisphere ; but the hope of being enabled to 

 examine the surface in the vicinity of this pole was unrealized on 

 account of the unfavorable weather. For this reason the limit of the 

 chart of 1881-82 does exceed 60 north latitude, and, hence, does not 

 extend much beyond the portions explored in 1879 ; but the parts 

 lying between 30 and 60 northern latitude could be more closely 

 examined. On this occasion also the lower end of the chart is limited 

 by a series of dark stripes which appear to be connected with the 

 northern ocean. The peculiar character of the surface of Mars can 

 not, however, be well explained until after the next opposition. It 

 was impossible to explore the southern ocean with exactness beyond 

 50 south, although all of the islands which had previously been recog- 

 nized were observed as white spots similar to the polar snow. All of 

 the smaller seas which branch off from the equator were very distinct 

 in their configuration. The continents and the interior lakes between 

 the bright equatorial zone and the south ocean could be drawn with 

 the greatest accuracy. A few changes in the appearance of particular 

 portions as compared with their shape in 1879 were noticed, and as 

 hundreds of thousands of square kilometres of surface, which were 

 formerly light, had in the mean while become dark, so on the other 

 hand many of the sections which previously were dark now became 

 luminous. These changes prove that the darkening principle which 

 produces them is due to something which is movable and extends over 

 the surface of the planet (for instance, water or some other liquid), 

 or perhaps something capable of being transmitted from place to 

 place (such as vegetation). 



Not one of the old dark lines which have been called " canals " 

 was missing, and causes which in all probability were due to the sun 

 produced numerous phenomena, which in former oppositions were 

 only suspected. That brilliant, light-red color mixed with white, 

 which in 1877 occupied the whole of the equatorial zone and a large 

 part of it in 1879, was found in 1882 to be entirely absent. Undefined 

 shadows began to form in this luminous veil surrounded by stains of 



