1900.] LOWELL—MARS ON GLACIAL EPOCHS. 659 
than with us, its relative absence causes a dearth of deposition which 
is the most important factor in establishing the conditions we have 
seen to exist. Lastly as a solid, the comparative lack of permanent 
ice-fields tends to keep the climate in a relatively genial condition 
and thus to allow the other two forms the greater play. Though 
the last seems but a passive partner, an acquiescer more than active 
accomplice, its 7déZe is not the least vital of the three. “There is no 
doubt that the climate of our own arctic and antarctic regions is 
boreal to an extent far surpassing what mere absence of sun could 
cause. It is the storage of ice, the actual cold locked up in that 
substance in those polar prisons that is the true climatic controller 
of the extreme north and the extreme south. 
23. From the mode of melting of the Martian polar caps, it is 
clear that we could have predicted a general dearth of bodies of 
water upon the planet from that evidence alone. We ought to 
have seen that so much was unmistakably written in the record 
open to our inspection. But other evidence presented itself first. 
So that we were already in possession of decisive testimony before 
the polar phenomena got a hearing. 
Already we had come to the conclusion that what were formerly 
thought to be oceans, the-blue green markings, were not in reality 
seas, but vast tracts of field or forest. Many things testified to 
this ; but not to weaken the argument by multiplying the proofs, 
it nay suffice to say that permanent dark lines traverse them, and 
coincidently traverse the idea that they can be seas. At the same 
time they change color with the season, as vegetation would do. 
As autumn advances they fade from green to gold, and with the 
spring grow green again. Our own forests could look no other 
viewed across the millions of miles of separating space. 
Change implies air, and vegetal change water to boot. Thus 
there is some water on Mars, though there is not much. 
24. After the phenomena of the maxima and minima of the caps, 
the next peculiarity connected with them is the eccentring of the 
southern one. And this distinction is the more significant from its 
not being shared by the northern. The northern cap sits squarely 
upon its pole. The southern, on the other hand, is markedly 
eccentric to the axis of rotation. Its centre lies some seven degrees 
from the geographical pole over toward a point in about longitude 
54°. Since then the two do not agree to differ, but are each 
idiosyncratic, it is clear that the cause cannot be one common to 
