i;38 Dr Hunt, Celestial Chemistry [Nov. 28, 



light, as deduced from the value of solar radiation and the 

 mechanical equivalent of the thermal unit. He concludes " that 

 the luminiferous medium is enormously denser than the continua- 

 tion of the terrestrial atmosphere would be in interplanetary space 

 if rarified according to Boyle's law always, and if the earth were 

 at rest in a state of constant temperature, with an atmosphere of 

 the actual density at its surface." The earth itself in moving 

 through space "cannot displace less than 250 pounds of matter." 



In 1870 W. Mattieu Williams published his very ingenious 

 work entitled The Fuel of the Sun, in which, apparently without 

 any knowledge of what had been written before with regard to an 

 interstellary medium, he attempts to find therein the source of 

 solar heat, the "solary fuel" of Newton. To quote his own 

 language, " the gaseous ocean in which we are immersed is but a 

 portion of the infinite atmosphere that fills the whole solidity of 

 space, that links together all the elements of the universe, and 

 diffuses among them light and heat, and all the other physical and 

 vital forces which heat and light are capable of generating " (loc. 

 cit. p. 5). 



Since the days of Newton, however, no one had hitherto con- 

 sidered the interstellary matter from a chemical point of view. 

 In 1874, as already shown, the writer had, in extension of the 

 conception of Humboldt that its condensation gives rise to 

 nebulae, ventured the suggestion that from an etherial medium 

 having the same composition as our own atmosphere the chemical 

 elements of the sun and the planets have been evolved, in accord- 

 ance with the views of Brodie, Clarke, and Lockyer, by a stoichio- 

 genic process, so that in the language of Newton's Hypothesis, " all 

 things may be originated from ether." 



It was not, however, until 1878. that, from a consideration of 

 the chemical processes which have gone on at the earth's surface 

 within recorded geological time, I was led to another step in this 

 inquiry. That all the de-oxydized carbon found in the earth's 

 crust in the forms of coal and graphite, as well as that existing iu 

 a diffused state as bituminous or carbonaceous matter, has come, 

 through vegetation, from atmospheric carbonic acid, appears certain. 

 To the same source we must ascribe the carbonic acid of all the 

 limestones which since the dawn of life on our earth have been de- 

 posited from its waters. It is through the sub-aerial decay of 

 crystalline silicated rocks, and the direct formation of carbonate of 

 lime, or of carbonates of magnesia and alkalies, which have reacted on 

 the calcium-salts of the primeval ocean, that all limestones and 

 dolomites have been generated. These, apart from the coaly mat- 

 ter, hold, locked up and withdrawn from the aerial circulation, an 

 amount of carbonic acid which may be probably estimated at not 

 less than 200 atmospheres equal in weight to our own. That this 



