_Lowell on the Purpose of the Canals._

Before leaving this subject it will be well to quote Mr. Lowell's own
words as to the supposed perfectly level surface of Mars, and his
interpretation of the origin and purpose of the 'canals':

"A body of planetary size, if unrotating, becomes a sphere, except for
solar tidal deformation; if rotating, it takes on a spheroidal form
exactly expressive, so far as observation goes, of the so-called
centrifugal force at work. Mars presents such a figure, being flattened
out to correspond to its axial rotation. Its surface therefore is in
fluid equilibrium, or, in other words, a particle of liquid at any point
of its surface at the present time would stay where it was devoid of
inclination to move elsewhere. Now the water which quickens the verdure
of the canals moves from the pole down to the equator as the season
advances. This it does then irrespective of gravity. No natural force
propels it, and the inference is forthright and inevitable that it is
artificially helped to its end. There seems to be no escape from this
deduction. Water only flows downhill, and there is no such thing as
downhill on a surface already in fluid equilibrium. A few canals might
presumably be so situated that their flow could, by inequality of
terrane, lie equatorward, but not all....Now it is not in particular but
by general consent that the canal-system of Mars develops from pole to
equator. From the respective times at which the minima take place, it
appears that the canal quickening occupies fifty-two days, as evidenced
by the successive vegetal darkenings, to descend from latitude 72° north
to latitude 0°, a journey of 2650 miles. This gives for the water a
speed of fifty-one miles a day, or 2.1 miles an hour. The rate of
progression is remarkably uniform, and this abets the deduction as to