On page 318 of F. M. Simpson's History of Architectural Development, vol. 1 (Longmans, 1956) I reprinted as fig. 107 the plan of Trajan's Forum from the earlier edition. I reprint it again here as Fig. 1. The plan is Lanciani's (Forma Urbis Romae, Milan, 1893, IV, 1). Compare R. Lanciani, Ruins and Excavations (London, 1897), fig. 119. This has drawn on me the strictures of scholars. Thus R. Martin writes (Revue des Études anciennes, p. 404, n. 1) that my book commits an ‘erreur dans le plan du forum de Trajan, qui ne rend pas la forme circulaire du côté méridional de la cour reconnu par G. Lugli’. By which he seems to mean that my plan makes the front wall of the court, to each side of the triumphal arch, straight and not segmental. A. von Gerkan, in Gymnasium, 1958, p. 545, remarks that in my book ‘gar zu oft hoffnungslos veraltetes Material vorgelegt wird. Das Trajansforum Abb. 107 ist ein groteskes Beispiel dafür’. Alas! following his usual custom, he gives no evidence for his statements, gladly though I should learn about these things.