434 [Feb. 12, 



expected to be the case, after the planet had increased his distance 

 from the earth to nearly double that when the observations began. 

 Adding to his own the experience of Mr. Lockyer, whose observa- 

 tions began 35 days earlier, this inference, of permanence in the 

 main boundaries of lights and shades, is extended to above 100 

 revolutions of Mars ; and on comparison of these with the earlier 

 sketches of Madler, Herschel, Jacobs, and De la Rue, the con- 

 clusion appears to embrace the whole series of more than thirty 

 years. 



The author regards as one of the main features very firmly 

 denned in the late opposition, the broad white or rather reddish 

 band which from about 65 of north latitude (the north pole being 

 invisible in these observations) spreads up into large bright cloud- 

 like prominences toward and beyond the equator, and retires into 

 one principal and several smaller bays toward the pole. From this 

 bright space, which in many parts is sharply defined, a broad dusky 

 tint spreads toward the south, partially relieved by half-lighted 

 expansions with shades of various depths between. The south pole 

 itself is surrounded (excentrically as it appears) by a bright white 

 mass, obviously glittering in the telescope. This is believed to be 

 snow ; and the effect of its whiteness is increased in most parts of its 

 circumference by the contrast of a dark ring round it, which ex- 

 pands here and there into broader spaces. Thus a great part of the 

 northern area appeared in the late opposition bright, and often 

 reddish, as if it were land, while a great part of the southern area 

 was of the grey hue which is considered to indicate water, but 

 relieved by various tracts of a tint more or less approaching to that 

 of the brighter spaces of the northern hemisphere. The principal 

 boundary of light and shade, for the most part very well defined, 

 ran obliquely across the equator of Mars, so as to reach latitudes 

 from 20 to 30 north and south of that line. This may perhaps 

 be understood by the drawings selected for illustration, especially if 

 compared with an orthographic projection of the latitudes*. (Still 

 better by means of the globes which accompanied the communica- 

 tion, constructed by the author, one from his own sketches, the 

 other from those of Mr. Lockyer.) 



* The inclination of the axis of Mars to the observer was, on the 1st of October, 

 1862, 25*, as Mr. Main has informed me. 



