360 



Mr. J. N. Lockyer. On the [May 6, 



fore, of the sun-spot curve must be restricted to a very large extent 

 to latitudes very near the equator, and this is the fact also, as is well 

 known. 



It will be seen that on this view, as the brightness and therefore 

 the temperature of the atmosphere as we know increases very con- 

 siderably from minimum to maximum, the masses which can survive 

 this temperature must fall from gradually increasing heights. 



It may be pointed out, how perfectly this hypothesis explains the 

 chemical facts observed and associates them with those gathered in 

 other fields of enquiry. 



At the minimum the ring is nearest the sun, the subjacent atmo- 

 sphere is low and relatively cool. 



Particles falling from the ring therefore, 'although they fall in 

 smaller quantity because the disturbance is small, have the best 

 chance of reaching the photosphere in the same condition as they 

 leave the ring, hence at this time the widening in many familiar lines 

 of iron, nickel, titanium, <fec. 



The gradual disappearance of these lines from the period of 

 minimum to that of maximum, is simply and sufficiently explained by 

 the view that the spot-forming materials fall through gradually 

 increasing depths of an atmosphere which at the same time is having 

 its temperature as gradually increased by the result of the action I 

 have before indicated, until finally when the maximum is reached, if 

 we assume dissociation to take place at a higher level at the maximum, 

 dissociation will take place before the vapours reach the photosphere, 

 and the lines which we know in our laboratories will cease to be visible. 



This is exactly what takes place, and this result can be connected 

 as I have stated elsewhere, with another of a different kind. This 

 hypothetical increasing height of fall demanded by the chemistry of 

 the spots is accompanied by a known acceleration of spot movement 

 over the sun's disk, as we lower the latitude — which can only be 

 explained so far as I can see by a gradually increasing height of fall 

 as the equator is approached. 



There are two other points. (1.) The sunspot curve teaches us that 

 the slowing down of the solar activities at the maximum is very 

 gradual. We should expect therefore the chemical conditions at the 

 maximum to be maintained for some time afterwards. As a matter 

 of fact they have been maintained till March of the present year, and 

 only now is a change taking place which shows us chemically that we 

 are leaving the maximum conditions behind. (2.) The disappearance 

 of the lines of the metallic elements at maximum is so intimately 

 connected with an enormous increase in the indications of the 

 presence of hydrogen, that there is little doubt we are in the presence of 

 cause and effect. The hydrogen, I am now prepared to believe, is a 

 direct consequence of the dissociation of the metallic elements. 



