GUNPOWDER. 191 



officers have affirmed that they have seen barrels of gunpowder 

 which was good in the morning, but which became (by attract- 

 ing, probably, the humidity of the air) entirely spoiled in the 

 evening. To keep the powder dry, by preventing the access of 

 the air, it has been proposed to line the barrels with tin foil, or 

 with thin sheets of lead, as tea boxes are lined. Would it not 

 be possible," asks Dr. Watson, " to preserve powder free from 

 moisture, and from the loss of a part of its sulphur in hot climates, 

 by keeping it in glazed earthen bottles, or in bottles made of 

 copper or tin, well corked ? The disposition to attract the 

 humidity of the air varies in different sorts of powder ; it is the 

 least in that which is made from the purest saltpetre. Pure 

 saltpetre, which has been dried as gunpowder is dried, does not 

 become heavier by exposure to the atmosphere ; at least, so far 

 as my experiments have informed me, not amounting to above 

 one seventy-second part of its weight. I rather think," con- 

 tinues Dr. Watson, " that it does not acquire any increase of 

 weight ; however, in order to judge with more certainty concern- 

 ing the effect of sea salt when mixed with saltpetre, in attracting 

 the humidity of the air, I made the following experiment : five 

 parts of pure saltpetre, in powder, were exposed for a month to a 

 moist atmosphere, but I did not observe that the saltpetre had 

 gained the least increase of weight ; for the same length of time, 

 and in the same place, I exposed four parts of saltpetre mixed 

 with one of common salt, and this mixture had attracted so 

 much moisture, that it was in a state of fluidity." 



Of all the powders which have fallen under my observation, 

 Messrs. Lawrence & Son's, of Battle, is the best. Some time 

 ago, a powder was pompously advertised, with "Sir Humphrey 

 Davy" attached to it, which did not answer the expectation in- 

 tended to be excited by the name of so great a chemist ; and 

 still farther to continue this feeling, the price was doubled. It 

 is probable, that Sir Humphrey Davy had nothing to do with 



