374 Original Articles. [July, 



snow masses, seen contemporaneously, one extended far around, or 

 rather in one direction from the south pole, the other near, but not at 

 the north pole, which was then presented to the sun. The snows near 

 the south pole must then have reached to the 40th degree south lati- 

 tude along one meridian. The interval between the snow of the north 

 and the south appears to have been about 105° ; while this interval on 

 the earth may be taken at 120°, so that the temperature of the surface 

 of Mars is not much lower than that of the earth, and perhaps is not 

 subject to such extremes of heat and cold, though this could hardly be 

 expected, since its revolution period is longer and its ecliptic more 

 oblique than in the earth. The surface of Mars, which is generally 

 free from snow, offers a great variety of distinct outline, which 

 separates bright parts from dusky or shady parts. In general a very 

 distinct, undulated outline of this kind can be traced along the inter- 

 tropical regions mostly south of the equator, from which a large tract 

 of bright surface spreads towards the north, while towards the south 

 for the most part, the surface is either distinctly greenish grey, or 

 appears in half lighted spaces, with less defined outlines than that 

 already referred to. Calling the grey parts sea, and the bright parts 

 land, the first impression on looking at Mars would generally be 

 that water prevails in the southern, and land in the northern hemi- 

 sphere. The land where broadest has a soft reddish tint, which resem- 

 bles the hue common in low " cumulus " clouds in the morning and 

 evening hours, or the diffused air tints in a foggy sunset.* Faint 

 Indian red is a good imitation. This colour of the surface fades 

 away in mere brightness towards the main southern boundary already 

 referred to, and is hardly to be traced at all over any part of the 

 smaller, and less distinctly bordered lands to the south. The white 

 brightness of the land along the main boundary is occasionally so 

 great, as in the meridian of 360°, as to suggest at first the idea of 

 snows, but a careful inspection removes this impression. The bright- 

 ness is in some degree enhanced in its effect on the eye, by the dark 

 spaces which lie in the grey tracts on the south side of the boundary. 

 This is observable in several parts, as represented in the chart, one 

 broad dark surface appearing about the equator in long. 20°, and 

 thence spreading with ramifications to the southward, and extending 

 down a narrow channel (180 miles wide) towards the north polar 

 region, which is apparently for the most part a watery surface ; ex- 

 cepting these instances the dusky spaces are not strongly marked, nor, 

 except in broad surfaces, is the greenish hue remarkable. Indeed, 

 during the opposition of 1862, several observers with achromatics did 

 not notice either the reddish tint of the land, or the greenish tint of 

 the water, but both were always seen when reflectors were used. 



It may now be fairly asked, whether the tracts of bright white 

 surface called snows are such ; the ruddy and bright surfaces really 

 land ; the grey shady spaces actually sea ? Whether all the lighter 



* Huygens noticed this and thought the land in Mars to be of " a blacker 

 colour than that of Jupiter or the moon, which is the reason of his appearing 

 of a copper colour and his reflecting a weaker light than is proportional to his 

 distance from the sun." 



