remarkable researches on the heat
of the moon and an investigation of the causes of its very low
temperature, I have, I think, demonstrated the incorrectness of Mr.
Lowell's results. In my last chapter, in which I briefly summarise the
whole argument, I have further strengthened the case for very severe
cold in Mars, by adducing the rapid lowering of temperature universally
caused by diminution of atmospheric pressure, as manifested in the
well-known phenomenon of temperate climates at moderate heights even
close to the equator, cold climates at greater heights even on extensive
plateaux, culminating in arctic climates and perpetual snow at heights
where the air is still far denser than it is on the surface of Mars.
This argument itself is, in my opinion, conclusive; but it is enforced
by two others equally complete, neither of which is adequately met by
Mr. Lowell.

The careful examination which I have been led to give to the whole of
the phenomena which Mars presents, and especially to the discoveries of
Mr. Lowell, has led me to what I hope will be considered a satisfactory
physical explanation of them. This explanation, which occupies the whole
of my seventh chapter, is founded upon a special mode of origin for
Mars, derived from the Meteoritic Hypothesis, now very widely adopted by
astronomers and physicists. Then, by a comparison with certain
well-known and widely spread geological phenomena, I show how the great
features of Mars--the 'canals' and 'oases'--may have been caused. This
chapter will perhaps be the most interesting to the general reader, as
furnishing a quite natural explanation of features of the planet which
have been termed 'non-natural' by Mr. Lowell.

Incidentally, also, I have been led to an explanation of the highly
volcanic nature of the moon's surface. This seems to me absolutely to
require some such origin as Sir George Darwin has given it, and thus
furnishes corroborative proof of the accuracy of the hypothesis that our
moon has had an unique origin among the known satellites, in having been
thrown off from the earth itself.

I am indebted to Professor J. H. Poynting, of the University of
Birmingham, for valuable suggestions on some of the more difficult
points of mathematical physics here discussed, and also for the critical
note (at the end of Chapter V.) on Professor Lowell's estimate of the
temperature of Mars.

BROADSTONE, DORSET, _October_ 1907.

TABLE OF CONTENTS.

CHAP