ly
brings in other possible explanations of the coming and going of
elevated surface features.

Finally, we may ask what about the reliability of the maps? About
this it is to be said that the most recent map--that by Lowell--has
been confirmed by numerous drawings by different observers, and
that it is,itself the result of over 900 drawings. It has become
a standard chart of Mars, and while it would be rash to contend
for absence of errors it appears certain that the trend of the
principal canals may be relied on, as, also, the general features
of the planet's surface.

The question of the possibility of illusion has frequently been
raised. What I have said above to a great extent answers such
objections. The close agreement between the drawings of different
observers ought really to set the matter at rest. Recently,
however, photography has left no further room for scepticism.
First photographed in 1905, the planet has since been
photographed many thousands of times from various observatories.
A majority of the canals have been so mapped. The doubling of the
canals is stated to have been also so recorded.[1]

The hypothesis which I have ventured to put before you involves
no organic intervention to account for the

[1] E. C. Slipher's paper in _Popular Astronomy_ for March, 1914,
gives a good account of the recent work.

198

details on Mars' surface. They are physical surface features.
Mars presents his history written upon his face in the scars of
former encounters--like the shield of Sir Launcelot. Some of the
most interesting inferences of mathematical and physical
astronomy find a confirmation in his history. The slowing down in
the rate of axial rotation of the primary; the final inevitable
destruction of the satellite; the existence in the past of a far
larger number of asteroids than we at present are acquainted
with; all these great facts are involved in the theory now
advanced. If justifiably, then is Mars' face a veritable
Principia.

To fully answer the question which heads these lectures, we
should go out into the populous solitudes (if the term be
permitted) which lie beyond our system. It is well that there is
now no time left to do so; for, in fact, there we can only dream
dreams wherein the limits of the possible and the impossible
become lost.

The marvel of the infinite number of stars is not so marvellous
as the rationality that fain would comprehend them. In seeking
other minds than