226 REPORTS ON THE STATE OP SCIENCE. 



heat derived from luminous flames to such purposes as glass ovens and 

 steel furnaces. The greater part of the paper was devoted to practical 

 considerations, but in the discussion which followed he expressed his 

 views as to the theory of the action, and stated that, in order to obtain 

 the best results, from the heat efficiency point of view, the operation 

 should be divided into two parts. In the first part chemical combina- 

 tion took place, the flame was luminous, and the heat should be 

 abstracted by radiation only. In order that the radiant heat might be 

 a maximum, there should be a larger space so that perfect combustion 

 could take place without the gases coming into contact with any 

 solid substance ; this space was the furnace proper. In the second 

 part there was no combustion, the flame was non-luminous, and the 

 heat should be abstracted from it by contact, as was done in the 

 regenerative part of the furnace. 



Siemens ascribed the radiant heat of the luminous flame to the 

 incandescent particles of carbon, and said that, since flame is trans- 

 parent to its own radiation, not only does the surface of the flame 

 radiate, but also its interior; hence a flame radiates far better than a 

 solid substance. ' A solid surface radiates only from its outer surface, 

 and from that surface only towards one a direction, while a flame radiated 

 from every point within it, and on its surface in every direction, or 

 from every point of its entire volume towards every direction. ' If the 

 area of a solid substance were doubled it would only radiate twice as 

 much, but if the surface of a (geometrically smaller) flame be doubled 

 the radiation would be four times as much. 



He specially called attention to the advantage of this method of 

 heating by referring to the experience obtained with glass pot furnaces 

 in Dresden and in Bohemia to which the new method of heating had 

 been applied. There were great gains in every direction : 50 per cent, 

 more glass for the same expenditure of heat, less breakage of pots, 

 the furnace lasted six times longer, and higher temperatures were 

 obtained, so that open pols could be used instead of closed ones. The 

 glass was produced from cheaper materials and was of superior quality. 



The statements made in the above paper were severely criticised by 

 German engineers, and therefore on October 26, 1884, Mr. Fr. Siemens 

 read a paper at a meeting of the ' Sachsischen Ingenieur und Architekten 

 Verein ' entitled, ' Gasflammofen mit freier Flammen-Entfaltung, ' 

 which was published in the ' Civilingenieur, ' 1884, and was prac- 

 tically a repetition of his previous paper. 



In October 1886 Mr. Fr. Siemens read another paper before the 

 Iron and Steel Institute, entitled ' Combustion with Special Reference 

 to Practical Requirements.' He confirmed what he had previously 

 stated, and added some remarks on dissociation, pointing out that if 

 flame came into contact with heated surfaces there was a tendency 

 to condense ' one or other of the constituents,' and that, therefore, 

 dissociation could take place at comparatively low temperatures ; hence 

 dissociation experiments should be carried out in large open spaces. 

 He also remarked that the Bunsen flame, being non-luminous, had but 

 little radiating power. 



1 This is not true unless possibly when the surface is perfectly polished. 



