266

XV. MARS AS SEEN ON AUGUST 16, 1909 }
} 314
XVI. MARS AS SEEN ON OCTOBER 29, 1909 }

NOTES ON THE MAPS AND CHARTS

The maps included in this work have been photographed from a globe of
Mars specially made for the purpose from various charts. In all the maps
the south is at the top and the north at the bottom; and the series
shows the general surface configuration all round the planet, together
with the principal canal lines which have been observed; but many other
canal lines exist, especially on the dark areas near the south pole.
These lines are usually straight and uniform in width throughout their
whole length: indeed it is difficult to mark them upon a globe so that
they shall appear as regular and uniform as they are actually seen on
the planet.

The names on the maps are those now generally accepted and used by
astronomers.

The "Greenwich" of Mars, _i.e._ the point on the Meridian from which
astronomers reckon the Martian longitudes, is indicated by the apex of
the small triangular light area just above the equator in Map I. It is
marked on the map as "Fastigium Aryn," and is chosen as longitude "0,"
because from its general outline it cannot be mistaken by observers.

"Sirapion," the supposed landing-place of the travellers mentioned in
the story, is shown on Map III., just above the central and lowest point
of the dark area at the top of the map. This name will not be found upon
any other map of Mars.

The chart showing the relative positions of the Earth and Mars during
the years 1909-10 is reduced and modified from one prepared accurately
to scale by the author for his own use in connection with the book. From
it the reader will gain a clear idea of the shape of the two orbits and
how they are placed with regard to each other.

It also shows the course supposed to be taken by the air-ship on its
outward and homeward journeys, and the point reached when one of the
travellers desired to turn back; together with the alternative routes
which were then discussed.

This chart, and the other one showing the positions of the two planets
at different oppositions of Mars, will enable the reader to understand
how it is that Mars approaches so much nearer to the earth at some
oppositions than it does at others. The positions of the oppositions
from 1916 to 1922 are only approximations, as no e