at the total solar Eclipse in 1882. 
73 
if we admit that the atmosphere absorbs at least as much heat 
as it transmits. But we know by every-day experience the far- 
reaching effects produced by what it transmits ; what does it do 
with the heat that it absorbs ? Do we see any evidence of work 
being done at the rate of two or even of one horse-power per sq. 
metre, remembering that the energy of storms is already accounted 
for? If it is absorbing heat at the rate of 2 gr.° C. per cm. 2 
per minute, how does it come that the atmosphere is so cool ? 
Again, looking to the length of time that the present state of 
things has existed, how has the atmosphere not long ago arrived 
at the state in which it emits as much energy as it absorbs, 
so that its effective power of absorption would be nil ? 
I do not ask these questions lightly. The subject has occupied 
my attention off and on for the last eighteen years, and I believe 
that the only answer to them is that the 'value of the solar 
constant which is now accepted is very much exaggerated . This 
view is, I think, supported by the following consideration. 
Taking the length of the sun’s radius as unity we have in 
the accompanying table the distance ( d ) from its centre to the 
sun’s surface, and to the three inner planets, Mercury, Venus, 
and the Earth, and the squares of these distances ( d 2 ). The 
Name of Body 
Sun’s 
surface 
Mercury 
Venus 
Earth 
Distance from Sun’s centre, d 
1-0000 
82-0646 
153-3466 
212-0000 
Square of Distance, c? 2 
1 
6,735-0 
23,515-0 
44,944-0 
squares of the distances represent the area on each planet over 
which the radiation per unit area of the sun’s surface is spread. 
It will be seen that the area on the earth’s surface covered by the 
radiation from a given area of the sun’s surface is almost double 
that covered by the same radiation on the surface of Venus, and 
therefore the intensity of radiation on Venus is almost exactly 
double that on Earth. In other words, the true value of the solar 
constant at a point on the orbit of V enus is almost exactly double 
its true value at a point on the earth’s orbit. It is impossible to 
believe that the cloudless atmosphere of the Earth, the whole 
mass of which is only 1 kg. per sq. centimetre, can produce an 
absorbing effect equal or superior to the dissipating effect of such 
a distance as that separating the orbits of Venus and the Earth. 
To conclude, it has been shown that under favourable meteoro- 
logical and geographical conditions, by the use of ordinary and 
necessarily imperfect mechanical appliances it is possible to 
