mall volume,
"Is Mars Habitable?" This was first commenced as a review of Professor
Percival Lowell's book, "Mars and its Canals," with the object of
showing that the large amount of new and interesting facts contained in
this work did not invalidate the conclusion that he (Wallace) had
reached in 1903--that Mars is not habitable. The conclusions to which
his argument led him were these:

(1) All physicists are agreed that ... Mars would have a mean
temperature of about 35 deg. F. owing to its distance from the sun.

(2) But the very low temperatures on the earth under the equator at a
height where the barometer stands at about three times as high as on
Mars, proves that from scantiness of atmosphere alone Mars cannot
possibly have a temperature as high as the freezing-point of water. The
combination of these two results must bring down the temperature of Mars
to a degree wholly incompatible with the existence of animal life.

(3) The quite independent proof that water-vapour cannot exist on Mars,
and that, therefore, the first essential of organic life--water--is
non-existent.

The conclusion from these three independent proofs ... is therefore
irresistible--that animal life, especially in its highest forms, cannot
exist. Mars, therefore, is not only uninhabited by intelligent beings
... but is absolutely uninhabitable.

* * * * *

In contrast to his purely scientific interest in astronomy, Wallace was
moved by the romance of the "stars," akin to his enthusiastic love of
beautiful butterflies. Had it not been for this touch of romance and
idealism in his writings on astronomy, they would have lost much of
their charm for the general reader. His breadth of vision transforms him
from a mere student of astronomy into a seer who became ever more deeply
conscious of the mystery both "before and behind."

"Rain, sun, and rain! and the free blossom blows;
Sun, rain, and sun! and where is he who knows?
From the great deep to the great deep he goes."

And whilst facing with brave and steady mind the great mysteries of
earth and sky, of life and what lies beyond it, he himself loved to
quote:

"Fear not thou the hidden purpose
Of that Power which alone is great,
Nor the myriad world His shadow,
Nor the silent Opener of the Gate."

Among the scientific friends to whom he appealed for help when writing
his astronomical books was Prof. (now Sir) W.F. Barrett.