43 



together is but small, and on the application of a slight dis- 

 turbing force, such as heat, friction, percussion, a breaking 

 up into simpler bodies takes place ; the products of explo- 

 sion are mainly, if not entirely gaseous, of large volume and 

 at a high temperature. 



On the other hand, in an Explosive mixture we have 

 certain ingredients " mechanically mixed," which can be 

 again separated, more or less completely, by mechanical 

 means, not involving chemical action. It must be noted 

 that, as a rule, the ingredients of an explosive mixture 

 have not separately explosive properties, but conjointly 

 work together, under certain conditions, to produce an 

 explosion. 



I will, for the present, neglect the Explosive Com- 

 pounds and consider, as being familiar to all, the most 

 prominent member of the second class. Gunpowder. 



Gunpowder is by no means a modern invention. The 

 Chinese are credited with a knowledge of it ages before its 

 re-appearance in Europe. In India we have evidence of the 

 use of Rockets from time immemorial, and in a M.S. of 

 the gth century, attributed to Marcus Groecus, and called 

 the " Liber Ignium," the proportions for a rocket composi- 

 tion are given : — one part sulphur, two of willow charcoal, 

 and six of saltpetre. Cannon was used by the English at 

 the battle of Crecy (1346), but without doubt its moral 

 effect in causing panic amongst men and horses largely ex- 

 ceeded the actual destruction caused by it. In the reign of 

 Elizabeth, the manufacture of powder was fairly established 

 in England, and the Crown constituted its manufacture a 

 monopoly. The proportions of constituents used varied 

 considerably at differenf periods, but on the establishment 

 of the Waltham Abbey Works, under Sir W. Congreve, 

 rapid strides were made towards its perfection. 



The ingredients used in Gunpowder are Nitre or Salt- 

 petre (XmOj), Brimstone or Sulphur (S.), and Charcoal 

 (nearly pure carbon.) 



The average proportions in which these are mixed in 



