/ of peftilential Difeafes. 65 Squares and Market-Places -, for whofoever hath been accuftomed to any Experiments with this Compofition, muft have perceived a much greater Shock given to the Air by its Explofion, than by the largeft Pieces of Ord- nance infomuch that if any Objection can [ie rgainft. the Practice of this in London, mould there be Occafion, it is the crafie Coir* dition of -the City Buildings, which perhaps may not well ftarid its Shocks, were they to be made with good Quantities of it at a time. THE Matter likewife of this Compofition in fome Meafure befpeaks its Ufefulnefs for thefe Purpofes on other Accounts, befides its Elaftich Force, becaufe it diiiufes into the Air great Quantities of that nitrous Salt, which is known to add much to its Serviceablenefs in Life : And whofoever confiders how much cheaper this is to be procured, and how much -eafier praclifed, than the firing off Guns, efpe- cially in the Middle of great Towns, cannot but be defirous to try it, in Cafe of fuch Ca- lamities as are now with too much Reaibn feared :, it may not therefore be unaccepta- ble to give its Compofition here. E W Sd
