24 Mr. Sturgeon on the Injlammation of Gunpo'wder 



the thickness of the aqueous column may be increased. When 

 the same jar is used with different intensities, then the lowest 

 intensity requires the thinnest strip of water ; not because the 

 intensity is lower, but because the quantity of fluid is less : 

 and although a column of water that answers for a low inten- 

 sity will answer for every intensity that is higher ; neverthe- 

 less, a column that would answer very well for a high inten- 

 sity, might be far too large, to insure success, with an inten- 

 sity that is very low. 



As glass tubes are both convenient and elegant for regu- 

 lating the diameter of a column of water ; about seven or eight 

 inches of barometer tube, y\j of an inch diameter, answers the 

 purpose very well, with any jar containing more than half a 

 square foot of coated surface on each side ; with any intensity 

 of charge above 50° per quadrant electrometer*. 



By employing a glass tube of the above dimensions filled 

 with water, and a jar containing 120 square inches of coated 

 surface on each side of the glass, gunpowder was ignited in 

 the circuit at every trial, with any intensity above 20°. When 

 two such jars were employed at the same time, gunpowder 

 ignited with every intensity above 10°; sometimes with an 

 intensity as low as 7° or 8°. The gunpowder was fine grained, 

 and of the best quality. If the gunpowder is bruised to a fine 

 powder, it will answer still better. 



When moistened thread, twine, or wood is used, any of 

 them may be cut in two, and separated a little, and the gun- 

 powder will take fire at this interruption of the watery part of 

 the circuit. Thus we learn that it is not necessary for me- 

 tallic conductors to be in contact with the gunpowder, to in- 

 sure its ignition by the electric fluid. 



A chain may be made of alternate links of copper wire and 

 tailor's thread, in such a manner as not to be easily distin- 

 guished from one that is all of metal. If such a chain be dipped 

 in water, and made a part of the electrical circuit, gunpowder 

 may be ignited in any part of that circuit, as though the 

 thread were one continued piece. 



When one of the above-mentioned jars was employed, and 

 a copper conductor formed the circuit, aether was fired at an 

 interruption, with every intensity above 20°. When the water 

 tube formed a part of the circuit, aether could not be fired, 

 though both jars were employed together, with an intensity 

 of 90°. 



* As quadrant electrometers do not afford uniform measures of electri- 

 cal intensity, but differ from one another according to the weight of the hall, 

 delicacy of suspension, &c. an intensity is here given, which, it is expected, 

 will answer with the generality of them. 



When 



