ix SCIENTIFIC MOTIVE 247 



of one per cent, of a compound of cerium. The whole 

 industry of the manufacture of incandescent mantles, 

 of which many millions are produced annually, has thus 

 arisen from purely scientific studies of the rare elements 

 thorium and cerium. 



Even the air-gas burner which gives a non-luminous 

 flame suitable alike for rendering an incandescent 

 mantle luminous or for heating purposes, was devised 

 and used for scientific work, and was later adapted to 

 everyday use. The inventor was R. W. von Bunsen, 

 the famous Heidelberg professor to whom chemistry is 

 indebted for important researches in every branch of 

 the science. Sir Henry Roscoe relates how he took to 

 the Heidelberg laboratory in 1853 a sample of the gas- 

 lamp which was used for heating purposes in the 

 chemistry department of University College, London. 

 The lamp consisted of an ordinary argand burner, above 

 which was a cylindrical copper chimney, on the top of 

 which was a disc of wire gauze. By this arrangement 

 a non-luminous flame was obtained, but the temperature 

 was often low, and in other respects the device was 

 unsatisfactory. Bunsen was not satisfied with this 

 lamp, and he said : " Roscoe, I am going to make a lamp 

 in which the mixture of air and gas shall burn without 

 any wire gauze." After making a large number of 

 experiments on the relative size of the openings for gas 

 and air, the Bunsen burner was produced in 1855. The 

 principle of this burner is used in every gas-fire and every 

 incandescent gas-lamp, as well as in numerous forms of 

 air-gas burners employed in various arts and manu- 

 factures. 



Calcium carbide has become a common substance on 

 account of its use in the production of acetylene for 

 house lighting and for motor and cycle lamps, and in 



