380 On a solar Calorimeter used in Egypt 



at the level of the sea. Further, in speculations connected 

 with physical meteorology we are not entitled to postulate 

 a more abundant supply. From this supply falls to be 

 deducted the energy of evaporation which however is returned 

 on precipitation, also the energy of storms which to a large 

 extent are secondary features attending the changing hygro- 

 metric state of the atmosphere. Notwithstanding the ap- 

 parently perfect transparency of the atmosphere on the 

 morning of the i8th we must admit that some of the energy 

 was lost by absorption in the passage through the earth's 

 atmosphere ; but the small effect produced by great variations 

 of the zenith distance of the sun on the rates observed shows 

 that this effect cannot be great, in fact it is entirely masked 

 by very slight motion of the air. Most recent writers put the 

 value of the solar constant at from 3 to 5 gr. C. per cm. 2 per 

 min., the greater part of which is added to the observed value 

 in order to compensate for the supposed absorption by the 

 air. Thus Scheiner 1 in a recent work writes : " From what 

 precedes it is apparent that the values which have been found 

 for the solar constant do not differ so very much from each 

 other. The older determinations have without doubt given 

 too small values, the later ones point with great certainty in 

 the direction that the solar constant is included between the 

 amounts of 3-5 and 4*0 gr. cal." Now even the lower of these 

 values can be true only 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 



1 Strahhmg tind Tcmperatur der Sonne, von Dr J. Scheiner : Leipzig, En- 

 gelmann, 1899; see P* 3^- 



