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 



Distance from Sun's centre, d 

 Square of Distance, d' 2 



Sun's 

 surface 



1-0000 



1 



Mercury 

 82-0646 

 6,735-0 



Venus 

 153-3166 

 23,515-0 



Earth 

 212-0000 

 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 Venus 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 



