94 MODERN SCIENCE READER 



bon on a cold surface, and if rendered non-luminous no 

 carbon can be obtained. These conclusions were imme- 

 diately accepted and were not seriously disputed until the 

 appearance in 1861 of a communication to the Royal Society 

 from E. Frankland. 



In this article Frankland advanced what has come to be 

 known as the "dense vapor" theory. He and his adherents 

 claimed that, although solid particles in a flame do cause it 

 to emit light, the light from our ordinary illuminating 

 flames is dependent to a great extent upon the presence of 

 dense, transparent, hydrocarbon vapors from which it is 

 radiated, and is not due to the presence of incandescent 

 solid carbon particles. They further claimed that the soot 

 deposited is not carbon, but a mixture of dense hydrocar- 

 bons of remarkably high boiling points. 



Frankland was led to take up his investigations by seeing 

 a report that candles burned at the same rate on the top of 

 Mt. Blanc as in the valley at its foot, and a second report 

 regarding the retardation of the bursting of shells with 

 time fuses at high elevations in India. 



Besides carrying on investigations in artificially rarefied 

 air in his laboratory, he climbed to the top of Mt. Blanc 

 with a goodly supply of standard candles and timed their 

 slow wasting away; probably keeping warm in the mean- 

 time by the fire of his enthusiasm. Many interesting facts 

 were brought to light by these investigations, but his use of 

 them in interpreting the causes of luminosity in ordinary 

 flames led him into error, and, although he found adherents 

 at the time, his views have long since been replaced by those 

 based upon more careful observation. The importance of 

 the work of Frankland lay not so much in what he did as 

 in what he led others to do ; and since the publication of his 

 views a great deal has been done by Heumann, Stein, 

 Smithells, Burch, Lewes and others. 



Stein disproved Frankland 's assertion that soot is a mix- 

 ture of dense hydrocarbons by showing that it cannot be 

 volatilized even by great heat, and that it contains only 



