LIFE ON VENUS 13 
conditions are not hopeful. Although an atmosphere 
exists, it appears to be extremely thin; water vapour 
seems to be present in only very limited quantity; the 
temperature is very low, and, except in the warmer 
portions of the planet during the summer season, 
would be insufficient to support life. The evidence 
suggests a frigid climate, with dust-storms whirling 
over vast deserts and salt seas frozen solid, while near 
the Poles land and sea alike are buried under snow. 
Summer produces a slight thawing, but even then the 
cold, salt-saturated soil would appear to be very un- 
favourable for plant growth. Arrhenius suggests 
that the presence of a low vegetation such as snow 
Algz near the Poles in summer is as much as could 
be hoped for under the conditions prevailing on Mars. 
Of the planets whose distance from the Sun is small 
enough to allow heat and light to reach them in 
quantity sufficient to permit of vegetation such as we 
know it, there remains Venus, and here at last we 
meet with conditions suitable for life. Venus possesses 
an atmosphere densely charged with water vapour, 
and maintaining a high temperature all the year 
round. The conditions prevailing there recall, in fact, 
those believed to have existed on the Earth during the 
Carboniferous Period, when our great deposits of 
coal, composed of the remains of tropical plants, were 
laid down in marshes and steaming lagoons; but on 
Venus the conditions are still more extreme—the 
temperature higher, and the moisture much greater, 
than those of Carboniferous times. If it is allowable 
to assume that the prevalence of physical and chemical 
conditions similar to those which in bygone ages 
supported an abundant vegetation on our globe, would 
