4 Experiments upon Gunpowder. 



were made in the barrel ; one of them, m^ even with the 

 bottom of the bore, and the other two at different dis- 

 tances from it. Any two of these vent-holes, as n and 0, 

 foV instance, being closed up by solid screws, a perfo- 

 rated screw, or vent-tube, v } was screwed into the third, 

 which served to contain the priming, and to convey the 

 fire to the powder lodged in the bore of the piece. 



Sometimes a longer vent-tube, represented by Fig. 4, 

 was made use of, which, passing through the powder in 

 the chamber of the piece, communicated the fire im- 

 mediately to that part of the charge that lay in the axis 

 of the bore. 



Another vent-tube, also, was used occasionally, which 

 differs in many respects from both those that have been 

 described. It is so constructed as to convey the fire to 

 the charge ; but as soon as the powder in the chamber 

 of the piece begins to kindle, and the elastic fluid to be 

 generated, the vent is firmly closed by a valve, and no 

 part of the generated fluid is permitted to escape. This 

 I shall call the vahe-Vent, and it is represented by Fig. 5, 

 upon an enlarged scale, that the parts of it may appear 

 more distinct. 



a, b, is a longitudinal section of a small portion of 

 the solid side of the barrel. 



c, d^ is the vent-tube, which is in all respects like the 

 short vent-tube commonly made use of, except only 

 that in this the end of the vent-hole (c\ which goes into 

 the chamber, is enlarged in the form of the wide end of 

 a trumpet or funnel. 



To this enlarged aperture the valve, v, is accurately 

 fitted, and by means of the small stem or tail, /, which 

 is fixed to the valve, and which passes up through the 

 vent-hole, and is connected with the spring, j, the valve 



