patronised. He argued that the sluggish current and the congestion on the lower courses of large navigable rivers, where urban centres are apt to develop, made the construction of mill-dams and mill- leats difficult and the use of the allegedly more efficient over-shot wheel almost impossible. Some mild caveats have been expressed by Dr. Edward Miller, looking out from the Master's Lodge at Fitzwilliam over the flats of Cambridgeshire where there were quite a lot of fulling-mills; 8 and Dr. Jennifer Tann has made an important reappraisal of the location of the very Gloucestershire mills which Miss Carus- Wilson made her own. 9 It still seems generally believed, however, that fulling-mills do require sharply falling country streams. Yet the power required for a fulling-mill is not significantly greater than that required for a grist-mill; and everyone knows that corn- mills abounded on the lower reaches of streams and rivers, inside towns, on fens, on estuaries and on the sea-coast, throughout medieval England and Wales. Furthermore, the notion that an over-shot wheel is necessary dies very hard. An over-shot wheel requires a stream of water falling on the top of the wheel, so there must be a natural or artificial fall in height between the water- supply and the mill. An under-shot wheel, where the water strikes the lower part of the wheel, is not dependent upon such a fall, although a steady flow of water is necessary and it was convenient to control this flow by the construction of a mill-dam or a leat. It is true that under-shot wheels are markedly less efficient than over- shot wheels in harnessing the kinetic energy of water (although the use of an inclined penstock can dramatically increase the head of water and therefore the efficiency of an under-shot wheel). 10 But an under-shot wheel with a controlled water-supply is perfectly adequate to power either grinding-stones or fulling-hammers, and the siting of mills was not therefore dependent on rapidly running hill-streams. 8 E. Miller, 'The Fortunes of the English Textile Industry during the Thirteenth Century', Economic History Review, 2nd. series, XVIII (1965), 65-72. 9 J. Tann, 'Aspects of the Development of the Gloucestershire Woollen Industry' (unpublished University of Leicester Ph.D. thesis, 1964); idem, 'Some Problems of Water Power-a Study of Mill Siting in Gloucestershire', Transactions of the Bristol and Gloucestershire Archaeological Society, LXXXIV (1965), 53 77. 10 Cf. L. Syson, British Water-Mills (London, 1965), pp. 76 82; Industrial Archaeology of Watermills and Waterpower (Project Technology Handbook, XI; London, 1975), pp. 18-22. The introduction of the inclined sluice is usually ascribed to Poncelet, a French engineer of the early-nineteenth century, who greatly improved the efficiency of under-shot wheels, but since an independent application of Poncelet's concept is found in a primitive Anatolian mill, the origin of the commonsense device is probably much older (H. H. Günhan Danisman, 'An Operational Fulling-Mill at Kirha-Divan in the Central Anatolian Plateau, Turkey', Post-Medieval Archaeology, XI , 80 85).