rcumstances, be evoked by
refraction as a kind of mirage.[1000] But none of these speculations are
really admissible, when all the facts are taken into account. The view
that the canals of Mars are vast rifts due to the cooling of the globe,
is recommended by the circumstance that they tend to follow great
circles; nevertheless, it would break down if, as Schiaparelli holds,
the fluctuations in their visibility depend upon actual obliterations
and re-emergencies. Fantastic though the theory of their artificial
origin appear, it is held by serious astronomers. Its vogue is largely
due to Mr. Lowell's ingenious advocacy. He considers the Martian globe
to be everywhere intersected by an elaborate system of irrigation-works,
rendered necessary by a perennial water-famine, relieved periodically by
the melting of the polar snows. Nor does he admit the existence of
oceans, or lakes. What have been taken for such are really tracts
covered with vegetation, the bright areas intermixed with them
representing sandy deserts. And it is noteworthy in this connection that
Professor Barnard obtained in 1894,[1001] with the great Lick refractor,
"suggestive and impressive views" disclosing details of light and shade
on the gray-green patches so intricate and minute as almost to preclude
the supposition of their aqueous nature.

The closeness of the terrestrial analogy has thus of late been much
impaired. Even if the surface of Mars be composed of land and water,
their distribution must be of a completely original type. The
interlacing everywhere of continents with arms of the sea (if that be
the correct interpretation of the visual effects) implies that their
levels scarcely differ;[1002] and Schiaparelli carries most observers
with him in holding that their outlines are not absolutely constant,
encroachments of dusky upon bright tints suggesting extensive
inundations.[1003] The late N. E. Green's observations at Madeira in
1877 indicated, on the other hand, a rugged south polar region. The
contour of the snow-cap not only appeared indented, as if by valleys and
promontories, but brilliant points were discerned outside the white
area, attributed to isolated snow-peaks.[1004] Still more elevated, if
similarly explained, must be the "ice island" first seen in a
comparatively low latitude by Dawes in January, 1865.

On August 4, 1892, Mars stood opposite to the sun at a distance of only
34,865,000 miles from the earth. In point of vicinity