Edward Carpenter — The Planet Mars. 
99 
raum of the Northern snow-cap, with tlie following results, the tiraes 
of year being again given in terms of our summer months : — 
May 4 
June 4 
17 
Diameter of spot 
31° 
28° 
22 ° 
24' 
0 ' 
54' 
July 4 Diameter of spot 18° 24' 
12 „ „ 15° 20' 
20 „ „ 18° 0' 
Here we remark tliat the numbers concerned are much larger 
than — more than double, in fact — what tbey are for the South Pole ; 
and we also remark a slower fall mg 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 away 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 bowever 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 its 
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 singulär confirmation of 
Mr. Murphy’s theory ; for, though the results may be exaggerated 
on that planet, yet for that very reason tliey point out the more 
distinctly in what direction we should look for corresponding results 
on our own planet. They teil us, in fact, in unmistakable langaage, 
that, other things equal, our Northern hemisphere would now be the 
glaciated one. For though I have not spoken of me-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 ränge of glaciation must lie within the summer ränge of snow, 
and that therefore the glaciated hemisphere must be that in which 
the summer ränge is largest, and the fiucfuations (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. 
