1903.] LOWELL—THE CARTOUCHES OF MARS. 368 
equator, but continues on into the planet’s southern hemisphere, 
the sign curvature changing when it crosses the line. 
Thus much of canal development the curves definitely state ; but 
we may infer more. 
Whatever constitute the canals, it is evident that their develop- 
ment proceeds from the pole down the disk, and, furthermore, 
that it advances over the surface at a fairly regular rate. It starts 
at the summer solstice; that is it follows the melting of the polar 
cap. ‘This suggests the source of the quickening. In consequence 
of the water then let loose the ‘‘ canals’? come into being. That 
this can be due to a bodily transference of matter, the water in ques- 
tion, seems negatived by the area concerned. More darkened area 
is gained than is lost. But this is not an easy point to be sure of. 
More forthright is the negativing of such transference by the time 
taken. Water would make its presence felt long before the actual 
darkening takes place. For at the latitude of 75°, the mid-latitude 
of the Arctic canals, the darkening begins on the day of the sum- 
mer solstice, which is considerably after the date of the most rapid 
melting of the cap. 
But though water directly does not account for the phenome- 
non, water indirectly does. A quickening to growth of some kind 
would produce the counterpart of what we see. And these statis- 
tics furnish us with a key to its character. It is a seasonal change, 
but a little consideration will suffice to show us that it is quite 
unlike in behavior the seasonal change we know on earth. 
Could we get off our earth and view it from the standpoint of 
space we should mark, with the advent of spring, a wave of ver- 
dure sweep over its face. If absence of cloud permitted of an 
unveiled view this flush of waking from its winter’s sleep would be 
evident, and could be watched and followed as it crept higher and 
higher up the parallels. Starting from the equator shortly after the 
sun turned north, it too would travel northward toward the pole. 
Here, then, we should mark, much as we mark it on Mars, a wave 
of darkening, the blue-green of vegetation superposed upon the 
ochre of ground, spreading over the planet’s surface; but the two 
would differ, the mundane and the Martian vegetal awakening, in 
one fundamental respect—the earthly wave travels from equator 
to pole ; the Arean from pole to equator. Clearly the causes com- 
pelling them differ. Yet are they both seasonal in character. To 
what then is the difference due? ‘To the presence or absence of 
moisture. 
