﻿Edward Carpenter — The Planet Mars. 99 



mum of the Northern snow-cap, with the following results, the times 

 of year being again given in terms of our summer months : — 



May 4 

 June 4 

 17 



Diameter 



of 



spot 



31° 



24' 



)) 





)) 



5) 



28° 

 2'2° 



0' 

 54' 



July 4 Diameter of spot 1 8° 24' 

 ■12 „ „ 1-5° 20' 



20 „ „ 18° 0' 



Here we remark that the numbers concerned are much larger 

 than — more than double, in fact — what they are for the South Pole ; 

 and we also remark a sloioer falling off towards the minimum. 

 There is more difficulty about the maximum. In the winter season 

 the edges of the spots, owing probably to the state of the atmosphere, 

 are ill-defined; and, as already hinted, when Mars is in opposition, 

 and therefore most favourably situated for observation, the wintry 

 pole is turned aioay from us, and therefore at no time is there any 

 opportunity of directly measuring the diameter of a snow-cap at its 

 maximum. It is however certain, as mentioned above, that the 

 maximum' of the Northern cap is nothing extreme, and in all 

 probability it is not far different from that of the Southern. 



Certainly, to one who looks at the more general aspects of the 

 question, nothing can be more obviously likely than that that should 

 happen which does happen at the two poles of Mars : namely that 

 that pole which endures the extremely hot summer and the ex- 

 tremely cold winter should present the extreme of fluctuation in 4ts 

 snow-cap, and that that pole which endures the moderately hot sum- 

 mer and the moderately cold winter should present a kind of modera- 

 tion or mean in the fluctuation of its snow-cap. And I believe that 

 the agreement of the behaviour of these caps with the more obvious 

 theory of the behaviour of snow under such circumstances was one 

 of the things which confirmed Maedler in the idea (for which con- 

 firmation is now no longer needed) that these white patches were 

 indeed snow. 



If Mars, then, gives us, in the variation of its polar snows, a true 

 result of astronomical causes, it gives us a singular confirnaation of 

 Mr. Murphy's theory ; for, though the results may be exaggerated 

 on that planet, yet for that very reason they point out tlxe more 

 distinctly in what direction we should look for corresponding results 

 on our own planet. They tell us, in fact, in unmistakable language, 

 that, other things equal, our Northern hemisphere would now be the 

 glaciated one. For though I have not spoken of ^Ve-caps — since we 

 have not such good reason for speaking of ice as of snow on Mars — 

 yet no one would I suppose doubt that, as Mr. Murphy points out, 

 the range of glaciation must lie within the summer range of snow, 

 and that therefore the glaciated hemisphere must be that in which 

 the summer range is largest, and the fluctuations (probably) least. 



However, other things are not equal ; and the able way in which 

 Mr. Murphy points out that the fact that " the climate of the 

 Southern hemisphere is on the whole maritime, and that of the 

 Northern continental," counteracts the effects otherwise natural to the 

 two hemispheres — that the geographical causes in fact overpower the 

 astronomical ones — must command the assent of most readers. 



There is one discrepancy, howevei^ in Mr. Murphy's second paper; 

 or an apparent one, probably due to a misapprehension on my part. 



