--Radiation due to scanty atmosphere not taken account
of
--Three independent proofs of low temperature and
uninhabitability of Mars
--Conclusion.


CHAPTER I.

EARLY OBSERVERS OF MARS.

Few persons except astronomers fully realise that of all the planets of
the Solar system the only one whose solid surface has been seen with
certainty is Mars; and, very fortunately, that is also the only one
which is sufficiently near to us for the physical features of the
surface to be determined with any accuracy, even if we could see it in
the other planets. Of Venus we probably see only the upper surface of
its cloudy atmosphere.[1] As regards Jupiter and Saturn this is still
more certain, since their low density will only permit of a
comparatively small proportion of their huge bulk being solid. Their
belts are but the cloud-strata of their upper atmosphere, perhaps
thousands of miles above their solid surfaces, and a somewhat similar
condition seems to prevail in the far more remote planets Uranus and
Neptune. It has thus happened, that, although as telescopic objects of
interest and beauty, the marvellous rings of Saturn, the belts and
ever-changing aspects of the satellites of Jupiter, and the moon-like
phases of Venus, together with its extreme brilliancy, still remain
unsurpassed, yet the greater amount of details of these features when
examined with the powerful instruments of the nineteenth century have
neither added much to our knowledge of the planets themselves or led to