Published online by Cambridge University Press: 05 July 2010
Masonry facing at 31 widely scattered sites was characterised by the comparative lithometric analysis of the linear dimensions, apparent areas and apparent proportions of random samples of 50 exposed building blocks. Typically, block length lies between three-quarters and one Roman foot and height from one-third to one-half of a foot. The mean proportions of blocks vary with the type of stone and range from 1.50 to 2.54, with ‘military’ builders tending to prefer low length:height ratios and stone that fractured in much the same way regardless of direction relative to the bedding (i.e. isotropic, near-isotropic). The evidence suggests that the choice of general-purpose stone and proportions by ‘military’ and ‘non-military’ builders varied over time with changing circumstances. Both kinds of builder seem to have been least selective in the late first and early second centuries a.d. and again in the late third and early fourth centuries.