THE FUEL OF THE SUN. 85 



suns, who inspire as they advance the breath of universal heat 

 and light and life ; then, by impact, compression, and radia- 

 tion, they concentrate and redistribute its vitalizing power ; 

 and after its work is done, expire it in the broad wake of their 

 retreat, leaving a track of cool exhausted ether the ash-pits 

 of the solar furnaces to reabsorb the general radiations, and 

 thus maintain the eternal round of life. 



But ere this a great difficulty has probably presented itself 

 to the mind of the reader. He will refer to the calculations 

 that have been made in order to determine the actual tempera- 

 ture of the solar surface and the intensity of its luminosity. 

 Both of these are vastly in excess of those obtained in our 

 laboratory experiments by the combustion of the elements of 

 water. Even taking into consideration the dissociated carbonic 

 acid whose elements should be burning in the photosphere 

 with those of water, and adding to these the volatile metals of 

 the solar nucleus whose dissociated vapors must, under the cir- 

 cumstances stated, be commingled with those of the solar 

 atmosphere, and therefore contribute to the luminosity by 

 their combustion, still by burning here on the earth a jet of 

 such mixed gases and vapors we should not obtain any 

 approach to either the luminosity or the temperature which is 

 usually attributed to the sun. 



I have made a few very simple experiments, the results of 

 which remove these difficulties. They were conducted with 

 the assistance of Mr. Jonathan Wilkinson, the official gas 

 examiner to the Sheffield Corporation, using his photometric 

 and gas-measuring apparatus. We first determined the 

 amount of light radiated by a single fish-tail gas-burner consum- 

 ing a measured quantity of gas per hour. We found when 

 another was placed behind this, so that all the light of the 

 second had to pass through the first, that the light of the two 

 (measured by the illuminating intensity of their radiations 

 upon a screen just as the solar luminosity has been measured) 

 was just double that of -one flame, three flames (still presenting 

 to the photometric screen only the smface of one) gave it 

 three times the amount of illumination, and so on with any 

 number of flames we were able to test. Mr. Wilkinson has 

 since arranged 100 flames on the same principle i.e. so that 

 the 99 hinder flames shall all radiate through the one presented 

 to the screen, thus affording the same surface as a single flame, 

 but having 100 times its thickness or depth, and he finds 

 that the law indicated by our first experiments is fully verified ; 



