308 Royal Society :—Mr. G. J. Stoney on the Physical 



opake substance, or a cloud of some transparent material which 

 scatters light abundantly. Both hypotheses are fully considered. 



To most of the foregoing conclusions relating to the photosphere 

 and the adjoining parts we may safely accord the probability 3, 



S. 



Polar calms and 

 ascending currents. 



Zone of variable winds produced by descending currents. 



\\ \\ 



Southern zone of variable winds produced by currents about to ascend. 



WW 



Equatorial zone of calms and descending currents. 



//// 



Northern zone of variable winds produced by currents about to ascend- 



Zone of variable winds produced by descending currents. 



Polar calms and ascending 

 currents. 



We have strong reasons for suspecting that the luminous clouds 

 consist, like nearly all the sources of artificial light, of minutely divided 

 carbon ; and that the clouds themselves lie at a very short distance 

 above the situation in which the heat is so fierce that carbon, in spite 

 of its want of volatility, and of the enormous pressure to which it is 

 there subjected, boils. The umbra of a spot seems never to form 

 unless when the region in which carbon boils is carried upwards, or 

 the hot region above the clouds is carried downwards, so as to bring 

 them into contact, and thus entirely obliterate the intervening clouds. 

 It is, however, not safe to attribute to the results stated in this 

 paragraph a probability of more than 1 . 



The trade -winds which blow over the surface of the photosphere 

 are also inquired into. These seem to arise, as Sir John Herschel 

 suspected, from the oblate form of the sun causing a difference in 

 the escape of heat from his poles and equator. There are ascending 

 currents at the poles, descending currents all round the equator. 



