Boil in water some brasil wood or Vermillion and a pound of chopped paper; and, when boiled for some time to draw out the colour, dry and meal it with a pound of sulphur, and eight pound of saltpetre. Or, to six pound of saltpetre, put one pound of sulphur, and half a pound of amber, and blood stone one pound. To make Yellow POWDER. Take eight pound of saltpetre, and one pound of sulphur, to which add one pound of wild saffron, that has been boiled in aqua vitæ, and afterwards made dry and mealed. To make GREEN POWDER. Boil two pound of rotten wood, with some verdegrease in aqua vitæ, then dry and pound it, and mix it with a pound of sulphur, and ten pound of salt-petre. To make Blue POWDER. Boil some indigo in aqua vitæ, with a pound of the bark of a young linden tree, then dry and reduce it to a powder, and mix it with a pound of brimstone, and eight pound of saltpetre. To make Pulvis Fulmanans, or Thunder in a Room. This composition is very simple, yet has a very curious effect; it is made of three parts of saltpetre, two of salt of tartar, and one of sulphur, all ground to a fine powder, and well incorporated together. As the effect of this powder is quite different to that of gun-powder, so is there a different method of firing it, which is thus: Put about two tea spoonfulls of it into a fire-shovel, or iron ladle, and set it over a slow fire, and when it is quite hot, it will go off with a violent report. There is something surprising in the nature of this composition; for as the common powder acts every way equal, and makes the greatest noise when confined, this, on the contrary, acts only downwards, and makes the strongest report when not confined. There is another sort of fulminating powder, called fulmanans aurum, on account of there being gold mixed in its composition, which is done by a chemical preparation; but as the preparing of the ingredients require a tedious and expensive process, I shall omit the method of doing it, and let those who chuse to make chemical experiments refer to authors on that subject, by whom they will find the manner of making this powder fully explained. It is said one grain of fulmanans aurum, when made to perfection, and held on the point of a knife, over a candle, will make a report louder than a musket. SECT. II. Of the SPUR-FIRE.