472 Mr. Frederick Siemens [May 7, 



brickwork filling them. As it is essential that the flame during its 

 first stage, while still in chemical action, should give up heat by 

 radiation only, it is found absolutely necessary that it should not 

 touch the sides or walls of the furnace chamber, or any material con- 

 tained in the furnace. The sides and arches of the furnace and the 

 flues leading into it must therefore be so arranged i\i?ii the flame does 

 not touch anything, and its length must be sufficient to allow time for 

 complete combustion before the flame leaves it. When regenerative 

 furnaces are arranged so as to fulfil these conditions the heat de- 

 veloped by the flame is much more intense than otherwise, while 

 notwithstanding the higher temperature and increased working power 

 attained, their durability is largely augmented. 



Intensity of temperature and durability are two advantages of the 

 greatest importance which were formerly seldom found combined in 

 furnaces. The manner in which these advantages are insured in 

 the radiation furnace may be thus explained : — 



Adopting the generally accepted theory of combustion, according 

 to which a flame consists of a chemically excited mixture of gases, 

 whose particles are in violent motion, either oscillating to and from each 

 other or rotating around one another, it follows that any solid substance 

 brought into contact with gases, thus agitated, must necessarily have 

 an impeding effect on their motion. Motion being the primary 

 condition of combustion, the latter will be more or less interfered with, 

 according to the greater or less extent of the surfaces which impede 

 the action of the particles forming the flame; in the immediate 

 neighbourhood of such surfaces the combustion of the gases will 

 cease altogether, because the attractive influence of the surfaces will 

 entirely prevent their motion ; further off, their combustion will be 

 partial, and only at a comparatively great distance the particles of gas 

 will be free to continue unimpeded the motion required to maintain 

 combustion. On the other hand, the surfaces themselves must suffer 

 from the motion of the particles of gas producing the flame, for 

 however small these particles may be, they produce, while in such 

 violent motion, an amount of energy wlaich acting constantly will in 

 time destroy the surfaces opposed to them, just as "continual 

 dropping wears away stone." This circumstance fully accounts for 

 the fact that the inner sides of furnaces, and the materials they con- 

 tain, are soon destroyed, not by heat, but by the mechanical, and 

 perhaps also by the chemical action of the flame. It would seem 

 strange that the heating power of a large volume of flame should be 

 so much interfered with by the contact of its outer parts only with 

 the inner sides of a large furnace chamber, if there was not another 

 cause besides imperfect combustion to reduce the heating effect of a 

 flame, which touches the surfaces to be heated. A flame when in 

 the state of combustion radiates heat not only from its outer surface, 

 but also from its interior by allowing the heat to radiate through its 

 mass. In this manner every particle of flame sends its rays in all 

 directions, but if the flame itself touches anywhere combustion ceases 



