.S7A- WILLIAM .SY/;.)//..V.s, F.R.S. 309 



also by terrestrial rotation, giving rise to an electrical discharge 

 tVoin the outgoing equatorial stream to the polar regions, where 

 the atmosphere to be pierced by the return flood is of least resist- 

 ance. Thus the phenomenon of the -aurora borealis or northern 

 lights would find an easy explanation. 



The effect of this continuous outpour of solar materials could 

 not be without very important influences as regards the geological 

 conditions of our earth. Geologists have long acknowledged the 

 difficulty of accounting for the amount of carbonic acid that must 

 have been in our atmosphere, at one time or another, in order to 

 form with lime those enormous beds of dolomite and limestone, of 

 which the crust of our earth is in great measure composed. It 

 has been calculated that if this carbonic acid had been at one and 

 the same time in our atmosphere, it would have caused an elastic 

 pressure fifty times that of our present atmosphere ; and if we add 

 the carbonic acid that must have been absorbed in vegetation in 

 order to form our coal beds, we should probably have to double 

 that pressure. Animal life, of which we find abundant traces in 

 these " measures," could not have existed under such conditions, 

 and we are almost forced to the conclusion that the carbonic acid 

 must have been derived from an external source. 



It appears to me that the theory here advocated furnishes a 

 feasible solution of this geological difficulty. Our earth being 

 situated in the outflowing current of the solar products of com- 

 bustion, or, as it were, in the solar chimney, would be fed from 

 day to day with its quota of carbonic acid, of which our local 

 atmosphere would assimilate as much as would be necessary to 

 maintain in it a carbonic acid vapour density balancing that of 

 the solar current ; we should thus receive our daily supply of this 

 important constituent (with the regularity of fresh rolls for break- 

 fast), which, according to an investigation by M. Reiset, communi- 

 cated to the French Academy of Sciences by M. Dumas on the Gth 

 of March last, amounts to the constant factor of one ten-thousandth 

 part of our atmosphere. The aqueous vapour in the air would be 

 similarly maintained as to its density, and its influx to, or reflux 

 from, our atmosphere would be determined by the surface tem- 

 perature of our earth. 



It is also important to show how the phenomena of comets could 

 be harmonised with the views here advocated, and I venture to 



