DISCHARGING OF ORDNANCE. 



519 



caloric, then we will maintain that the flame, 

 though capable of insulation to a certain extent, 

 yet has a strong attraction for all kinds of matter, 

 and has a tendency to extend itself from particle to 

 particle of such bodies as come in contact with it. 

 Its particles, too, have a strong repulsion for each 

 other, and facilitate the diffusion. Hence as we 

 lengthen the tube, we increase the surface of attrac- 

 tion, till we entirely diffuse the flame. It is so far 

 favourable to this supposition, that air does not be- 

 come luminous, when united with a great quantify 

 of caloric; and it has even been observed, that air 

 has remained invisible, although heated to such a 

 degree as to inflame substances upon which it was 

 allowed to act. The following experiments seem 

 calculated to elucidate one or other of these theo- 

 ries with regard to caloric. 



Experiment %5. — Let a tube be affixed to the 

 apparatus, of such a length only as just admits 

 of the flame passing out at the bottom. Let the 

 interior be made quite resplendent, by wiping away 

 the smoke, moisture, &c. from its surface. Let a 

 given weight of the fulminating powder, say exactly 

 one grain, be used at each trial, and regulate the 

 blow as well as possible, that it may be nearly of the 

 same force each time. Examine, in several dis- 

 charges, cleaning the interior of the tube each time, 

 if the flame passes through the whole length, and 

 appears at the bottom. Then try the following : 



