t of the Martian year; whilst the central portion becomes fainter but
does not disappear.

"Of course it was at once declared that these oases were illusions which
would naturally be seen where two lines crossed each other and were
viewed from a great distance. But they only occur in some cases at such
crossings, and there are many junctions without any oases. Moreover,
they are also seen between the double canals where there are no
junctions nor anything which could give rise to illusion.

"At Flagstaff Observatory it was also noted that the canal lines
themselves underwent seasonal changes. Those viewed during the winter
season were always so faint as to be scarcely discernible, but at the
period when vegetation would naturally begin to grow they became more
easily visible, and still more distinct as the season advanced.

"Then Professor Lowell announced his great conception, which has given
rise to so much controversy, and has also been much misunderstood and
misrepresented.

"Briefly, his conclusions were as follows:--'Science teaches that a
small planet will become cool and develop life much sooner than a large
one. Similarly a small iron casting will become cool in a few days,
whilst a large one will be many weeks or even months in cooling. A small
planet will also develop more rapidly, and reach its final stage when it
will be incapable of supporting life, very long before a larger planet
like our earth will have reached that stage. Applying this to Mars, a
much smaller planet than our earth, it is scientifically reasoned that
Mars has passed through nearly all its stages and is approaching its
last. It has lost much of its atmosphere, all its large bodies of water,
such as oceans or seas, and, as regards the land, that has become
levelled by erosion, and about five-eighths of the whole area has become
desert.

"'Science also shows that in such circumstances rain would cease to fall
over the larger part of the planet, but the water vapour in the air
would be carried by natural circulatory currents of air to the polar
regions, and there deposited in the form of snow or hoarfrost, thus
forming a large snow-cap at the north pole in one season of the year,
and a still larger snow-cap at the south pole in the opposite portion of
the year.

"'These snow-caps would begin to melt in the spring as soon as the tilt
of the planet brought the pole to the position where the sun would take
effect, and would continue dur