Richard Penfold Richard W. Penfold "Lady of the Lea" Explosives BargeRichard W. PenfoldCopyright Richard W. Penfold 1978Oil on canvas For over three centuries, explosives barges carried their awesome cargo from the Mills at Waltham Abbey to the Woolwich Arsenal and the Government Magazines at Purfleet, via the river Lea and Thames. Road traffic across the bridges of the Lea was usually suspended as the barge passed beneath, for fear of embers (from steam driven vehicles) and other discarded means of ignition dropping onto the deck of the passing barge. Smaller craft, depicted in the illustration, were used to transport explosives materials between the various process buildings on the Royal Gunpowder Mills site, along an intricate network of narrow canals. Gunpowder Incorporating Mill (c.1780)Richard W. PenfoldCopyright Richard W. Penfold 1978Oil on canvas Each millstone weighed approximately 3 tons and the ingredients of Sulphur, Charcoal and Saltpetre were milled for up to 5 hours, in batches of 50 lbs. The incorporated mixture was known as millcake.