In archaeological mapping, just as in its other fields of work, the British Ordnance Survey leads the world. Nationalistic as it sounds, this plain statement of fact need not offend our brothers in other countries: they could without any doubt all do as well, although often indeed not easily. Not easily, because behind a great Period Map like this, and its predecessors for Roman and post-Roman times, there runs throughout the Survey’s history, and through the last forty years pre-eminently, its steady tradition of archaeological recording on the ordinary large-scale sheets. This is carried in unexampled measure to the popular smaller-scale editions, but neither that nor the Period Map production would be practical possibilities without the fundamental large-scale work, year in year out carried on by the Survey’s Archaeology Division. The forty years since it was set up, in the form of O. G. S. Crawford single-handed, are divided into almost equal halves by the great destruction at the Southampton office in 1941. Hard recovery and big development have ensued throughout the Survey; but in this Division the recovery was particularly hard, and the development has had to be relatively big, to produce a unit of workmanlike capacity, small though this is amongst the.rest. Before praising the new map in all its excellences, then, let us remember that like all its kind, it is the fruit not only of special but of incessant ordinary work performed in the routine of the Division, patient yet intensive. The ill-informed gaucherie of a recent Government remonstrance on this intensiveness has already been answered by ANTIQUITY, in the name of all sensible opinion; one must hope it will now be quietly laid aside. The intensiveness is no less needful than the patience; and Mr Charles Phillips, the Division’s chief all through these years, fully merits his high reputation on both counts.