1 Cement or hydraulic mortar made by mixing lime with reactive siliceous material (in the form of crushed tiles or volcanic ash), later developing superior strength and water-resistance, used by the Romans.
2 Parker's or Sheppey hydraulic cement, manufactured from c.1796 using septaria (nodules containing networks of mineral-filled cracks) from Harwich, Essex, and the Isle of Sheppey. The calcareous clay nodules were crushed and burnt, then mixed with lime, sand, and water. Setting quickly and hard, it was brownish in colour, and was much used in C19 as a render for walls, often scored to resemble ashlar joints. See also pozzolan.
Gwilt (1903);Nicholson (1887);W. Papworth (1887)