seldom complete. The most important economically are the Middle Coal Measures up to 2,000 feet thick. Relief is dominated by the marine-eroded surfaces. (a) Lower Coal Measures — Holywell Shales and Gwespyr Sandstone with very little coal and none economic to work. (b) Middle Coal Measures-mainly grey shale and clay with some sandstone and about 18 workable coal seams from one to 131 feet thick (totalling 77 feet). The Main coal (usually 6 to 11 feet thick) has been the most important. Generally, where the Main coal was absent, workings were short-lived. In Flintshire the Main coal underlay only 20 square miles of the 60 square miles forming the coalfield. (In Denbighshire, the Main coal underlay 70 square miles of the total 86 square miles.) Early coal workings were small and spasmodic but development was rapid. In 1570 total production was 100 tons, by 1593 exports alone were 1,000 tons reaching 12,000 a year by 1681. The Commission on Coal Measures in 1616 states that the principal workings were Wepre, Bagillt, Uphyftton, Leaderbrook, Englefield and three at Mostyn. Mostyn exported over 100 tons a month3. There were other mines, e.g. Aston and Leeswood. Most mines were still shallow adits or bell pits, though some were getting deep enough to have water drainage and ventilation problems, e.g. Mostyn and Bagillt. However, miners were still mainly engaged in agriculture. Thus, during important agricultural seasons, mining was neglected. Settlement was dispersed and related to agricultural holdings (though the population was denser than could be supported by agriculture alone). There were some full-time miners, e.g. a colony of Englishmen was attracted to Bagillt and an "English preacher employed for them"4. This type of influx would almost certainly settle close to the mines but there is a lack of in- formation indicating numbers or the degree of permanence. Slow development in the Mancot, Buckley and Mold areas was mainly due to problems of transport. By mid-eighteenth century the establishment of the brick industry (14 concerns around Buckley mountain, and it spread to Mold, Bagillt, Northop and even Mostyn) and the canalisation of the River Dee between Chester and Connah's Quay resulted in great expansion of eastern areas, e.g. Little Mancot and Great Mancot mines and others in the Mancot area (with provision of workmen's cottages in Mancot), Pentr- obin, Barmel and Woods mines. In the Mold-Leeswood area cannel coal was worked for oil distillation. Above the coal seams in the Buckley district is a localised fine grained siliceous bed and marl- the Buckley fireclay-used in making fine and acid-resistant bricks. Other fireclays used in brick and earthenware manufacture occur beneath some coal seams. There are three areas relatively drift-free along Alltami Brook (unworked) a belt from Castle Brickworks to just east of Buckley; and an area between Ewloe Hall and Lane End. The last two have been the main locational factor for the brick and pottery industries and their associated settlements. The Buckley Plateau is a severely-dissected surface 500 feet O.D. bounded in the 3J. U. Nef, The Rise of the British Coal Industry (1932), VoL 1, pp. 55, 109 N.L.W., Bettigfield MSS 715, 719 Wynn (of Gwydir) Papers, MSS. 2249,1469. ♦N.L.W., Henry Taylor MS. 6281F.