DISCHARGING OF ORDNANCE. 



521 



materiality of the flame, independent of the air. 

 The clear surface reflects the flame, and, therefore, 

 does not retard its motion ; the blackened surface 

 absorbs the flame, and therefore retards its motion : 

 but the air is affected nearly in the same degree by 

 both surfaces ; therefore, it should produce the same 

 mechanical effects upon the paper at the bottom, 

 whether the interior be resplendent or blackened. 

 If the flame passes through the same length of the 

 tube, without any regard to the colour of the sur- 

 face, then we may maintain that it is the power of 

 the combination that prevents the flame leaving the 

 air, to display its natural character of absorption by 

 a black surface ; at the same time also, the velocity of 

 the flame itself may have a tendency to retain it in an 

 insulated form. But if we find, that, by blackening 

 the inner surface, we stop the progress of the flame, 

 we are entitled to assume, even although the air 

 still pass from the bottom of the tube and tear the 

 paper, that there has here been a quantity of free 

 caloric passing along, quite independent of the quan- 

 tity retaining in the constitution of the air. But, 

 again, if we find, upon trying Experiments 27, and 

 28, that the paper at the bottom is torn, at a great- 

 er distance from the top, when the interior is re- 

 splendent than takes place when it is blackened, 

 then we have it clearly shewn that the flame has 

 been producing these effects in an insulated form ; 

 for had the tearing of the paper been the effect of 

 the motion of a quantity of air, then we should have 



