All difficulties dissolve and speculations become needless under one condition only:  that in which rationality may be inferred directly or indirectly by our observations on some sister world in space, This is just the evidence which in recent years has been claimed as derived from a study of the surface of Mars.  To that planet our hope of such evidence is restricted.  Our survey in all other directions is barred by insurmountable difficulties.  Unless some meteoric record reached our Earth, revelationary of intelligence on a perished world, our only hope of obtaining such evidence rests on the observation of Mars’ surface features.  To this subject we confine our attention in what follows.

The observations made during recent years upon the surface features of Mars have, excusably enough, given rise to sensational reports.  We must consider under what circumstances these observations have been made.

Mars comes into particularly favourable conditions for observation every fifteen years.  It is true that every two years and two months we overtake him in his orbit and he is then in “opposition.”  That is, the Earth is between him and the sun:  he is therefore in the opposite part of the heavens to the sun.  Now Mars’ orbit is very excentric, sometimes he is 139 million miles from the sun, and sometimes he as as much as 154 million miles from the sun.  The Earth’s orbit is, by comparison, almost

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a circle.  Evidently if we pass him when he is nearest to the sun we see him at his best; not only because he is then nearest to us, but because he is then also most brightly lit.  In such favourable oppositions we are within 35 million miles of him; if Mars was in aphelion we would pass him at a distance of 61 million miles.  Opposition occurs under the most favourable circumstances every fifteen years.  There was one in 1862, another in 1877, one in 1892, and so on.

When Mars is 35 million miles off and we apply a telescope magnifying 1,000 diameters, we see him as if placed 35,000 miles off.  This would be seven times nearer than we see the moon with the naked eye.  As Mars has a diameter about twice as great as that of the moon, at such a distance he would look fourteen times the diameter of the moon.  Granting favourable conditions of atmosphere much should be seen.

But these are just the conditions of atmosphere of which most of the European observatories cannot boast.  It is to the honour of Schiaparelli, of Milan, that under comparatively unfavourable conditions and with a small instrument, he so far outstripped his contemporaries in the observation of the features of Mars that those contemporaries received much of his early discoveries with scepticism.  Light and dark outlines and patches on the planet’s surface had indeed been mapped by others, and even a couple of the canals sighted; but at the opposition of 1877 Schiaparelli first mapped any considerable

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