88 Col. Gibbs on Gunpowder. 



from near the fire to the corner of the room, produces a coH' 

 siderable change in its weight. I presume, therefore, that 

 the lime, which in its caustic state has also a great affinity to 

 water, attracts a portion of it from the powder, and leaves it 

 in a state of dryness best fitted for inflammation. But if the 

 lime should remain too long mixed with the powder, it would 

 probably attack the water of crystallization of the saltpetre, 

 and, according to Count Rumford's idea, destroy a great part 

 of the power. If also left exposed, attractions of moisture would 

 take place from the atmosphere, the gunpowder would remain 

 surcharged with humidity as before, and the lime would be 

 only an inert mass. 



The examination of this subject led me to consider the in- 

 crease of the power of gunpowder in various situations, and of 

 its use in the field. It is well known that after a few dis- 

 charges a cannon becomes heated, and the range is much 

 greater, as well as the recoil. The charge of powder is there- 

 fore reduced about one quarter, to produce the original effect. 

 As I have not heard or seen any explanation of this fact I shall 

 take this opportunity of mentioning, that it appears to arise 

 from the same cause as the first explained, viz. the desicca- 

 tion of the powder. No person will dispute the heat acquired 

 by a cannon, or even a musket, after repeated discharges ; and 

 this heat must volatilize or destroy a great portion of the mois- 

 ture combined with the powder, assist its speedy inflammation, 

 and perhaps add to its power, by causing a more perfect com- 

 bustion of the inflammable parts of the gunpowder. This 

 would cause a much greater volume of gas to be produced, 

 and the high temperature would also greatly augment its elas- 

 ticity ; and it is well known that the effects of gunpowder 

 depend upon the rapid production and high degree of elasticity 

 of a great quantity of aeriform fluids or gases. 



