POWDER. 93 



The proper " epreuvette" is very correctly made; 

 the wheel on which the gradations are marked is large, 

 and the spring strong ; consequently the resistance to 

 the force of the powder is considerable. The stronger 

 it is the better; for without the resistance is strong, a 

 correct proof cannot be obtained ; because, if not suf- 

 ficiently strong to detain the powder in the chamber long 

 enough for all the particles to ignite, many of them 

 (especially in powder of good firm grain) willjly off 

 unburnt, and, of course, a part only of the charge 

 would be proved. 



The part, attached to the wheel of the epreuvette, 

 which shuts the mouth of the chamber, should be so 

 nicely adjusted, that on looking closely at the parts, 

 when in contact, no light can be seen between them ; 

 for, if any light, there is of course so much vacancy, 

 and consequently so much windage; and, in proportion 

 to the windage, the proof will be lower; and, therefore, 

 incorrect. 



Three fires, at least, should always be made in proving, 

 and the average taken as the mean amount ; for varia- 

 tions frequently happen in fires immediately following 

 each other, although made with considerable attention. 

 Care should be taken, after every fire, to clean the 

 chamber nicely, or otherwise the foulness left by the 

 preceding discharge would lessen the space, by which 

 the succeeding charge would become proportionally less. 



The best powder for copper-cap guns is the "fine 

 cylinder? because with them the large-grained powder 

 is so liable to miss fire. But with copper primers we 

 may venture on that of larger grain ; and particularly 

 in damp weather or on salt water. But by experi- 

 ments, in 1829, I find that the size in grain of the 



