ROMAN URBAN TOPOGRAPHY in Britain and the western Empire

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Dilke: Ground survey and measurement in Roman towns Fig 13 Bronze mitre square (norma) found in Watling Street, Canterbuy, in 1978, probably 2nd-century (Width: 162 mm) military camp was called gromae locus (ps-Hyginus), and that the only undoubted groma extant is the one whose metal parts were found in the workshop of Verus at Pompeii (Della Corte 1922). This particular groma might, therefore, have been used either for urban or for rural survey. The decempeda (Fig 12), measuring ten pedes monetales, would be of use for all types of survey, while the chorobates served certainly for aqueduct- and probably for road-survey. The norma, set square, similar to the mitre square of which an inscribed specimen was found at Canterbury (Hassall & Tomlin 1979, 350-l; Chapman 1979) (Fig 13), was of most use to the architect and building surveyor. The dioptra, a complicated astronomical or surveying instrument described by Heron of Alexandria, does not seem to have been in general use, but it is probable that the portable sundial (Price 1969; Dilke 1971, 70-2) was useful for orientation as well as timekeeping. The model in the Oxford Museum of the History of Science includes Britain among the provinces whose latitudes are recorded on the reverse (Fig 14). Units of measurement were affected by two factors: (a) size and type of survey, and (b) local usage. Roads were normally measured in miles, and may in some cases have been surveyed in 1 -mile lengths. Distances on Hadrian’s Wall were measured in some areas in feet, in others in passus. Centuriation schemes were measured in actus of 9 120 feet, and the sides of ‘centuries’ are always quoted in integral numbers of actus, most commonly 20 (Fig 15). But the width of limites between the ‘centuries’ is always quoted in feet, again in integral numbers, such as 8, 12, 20; and we may take it that this applied also to town streets. For building- or room-measurements too, feet were used, and on plans they appear as integral numbers. The same is true of burial plots, mostly just outside towns and normally in round numbers of feet. The merides, ‘lots’, in Orange (see above) were in feet, including half feet, and the total of merides III-VI comes to a round number, 200 feet (Piganiol 1962, 333). Solaria were calculated in square feet. Examples of local usage in ancient metrology are numerous (Hultsch 1882). In Gaul roads were measured not in miles but in leagues, 1 league being 1½ Roman miles. We are also told by Columella (v.1.6) that ‘the Gauls call a length of 100 feet in urban areas a candetum, and in rural areas a length of 150 feet’; to which Isidore (Origines, xv. 15.6) adds that in rural areas a square with sides of 150 feet is called a iustum candetum. Likewise there was a local Italic variant, the vorsus of 100 feet. Moreover, the basic unit, the foot, varied appreciably, the Ptolemaic foot of Egypt and Cyrenaica being 12½ inches and the pes Drusianus 13½ inches of the pes monetalis. The pes Drusianus was used in Germany and parts of Gaul, but
Dilke: Ground survey and measurement in Roman towns Fig 14 Portable sundial in the Oxford Museum of the History of Science, probably 3rd century AD. This type was designed for use at all latitudes, and has those of many provinces inscribed on the reverse (Britain is at 57º) recent attempts to prove its use elsewhere have not, as shown by Duncan-Jones (1980) and Millett (1982), been entirely conclusive. Frere (1977, 92; cf Walthew 1981 b) has rightly pointed out that the outer insulae at Amiens measure 4 by 4 actus in pedes Drusiani; though if at Vetera I, near Birten, the insula south of the principia is 375 by 330 pedes Drusiani, should we not leave it at that, rather than convert it to 3 by 2 actus (Frere 1977)? Similarly, it does not follow that for the ‘proto-forum’ in London the overall exterior length envisaged by the Romans was 3 actus in pedes Drusiani (ibid, 101-2). The measurement given is 106.7m, which comes to 355 rather than 360 pedes Drusiani, and even that only if we include projections. Round numbers in Roman buildings seem on the whole to refer to inside measurements wall to wall, but the application of actus to buildings is a doubtful proposition in any case, hardly proved by a house at Cambodunum (Kempten) adduced by Walthew (1978, 342). 1 How then were Roman towns planned and surveyed? Detailed instructions are provided by Vitruvius, some of which would chiefly concern the architect, some the surveyor. For a new town, he writes (i.4), first a good site should be selected, aspect, health, and defence being considered (see Salway, this volume, pp 67-8). For defence, town walls should not be square or with projections, but should have a circuit wide enough for two men to pass (i.5.2-3). Before building them, the architect should see that ‘roads duly laid out, convenient rivers, or supplies by sea through harbours ensure adequate building material for the ramparts’ (i.5.1). We may note that nearby water was not indispensable, as aqueducts could be built (viii.5-6). Both the architect and the surveyor should master ichnographia (i.2.2), the drawing, presumably on papyrus, parchment, or wax tablets, by rule and compasses, of a ground plan. Town streets should be planned first, then the forum (i.7). In a seaside town the forum should be by 10 the harbour; elsewhere it should be central. Next the theatre site should be chosen (v.3). Temple sites should be fixed with due consideration for the deity involved (i.7.1-2). For baths as warm a site as possible is advocated (v. 10.1). As preparations for his ichnopaphia Vitruvius gives certain ideal proportions. The forum should not be square, like the Greek agora (this of course is a generalization), but rectangular (v.3), his prescription being a proportion of 3:2. He prefers to adhere to the traditional layout of many Roman towns by siting gladiatorial shows in the forum, rather than by constructing an amphitheatre, which he barely mentions. The basilica, he says, should adjoin the forum on as warm a side as possible, its breadth being from a third to a half its-length. He had himself designed one, perhaps in c 30 BC, at Fanum Fortunae (Fano), with a nave measuring 120 by 60 Roman feet between the columns and a porticus 20ft wide between the columns and the wall (v. 1.6). Vitruvius also gives proportions for the caldarium of baths, 3:2 excluding the apse, and for the triclinium, 2:l. Since the basilica measurements, evidently actual as well as theoretical, involve round numbers, one might imagine that this would be true of rooms in houses too. In fact this is not so, since Vitruvius gives a series of ratios, depending on the length of the atrium, for the widths of the alae and tablinum (vi. 3.3-S). Thus for atrium lengths of 35, 45,55,70, and 90 Roman feet, the widths of the alae will be 11.67, 12.86, 13.75, 15.56, and 18 Roman feet respectively. These figures are only theoretical, but they show that, even though an architect may have liked to start Fig 15 Units of area measurement in Roman land surveying. Above: 1 iugerum = 2 actus quadrati = 2 x 1 lineal actus; 1 lineal actus = 120 Roman feet. Below: 1 centuria = 200 iugera = 400 actus quadrati = 20 X 20 lineal actus
Page 1 and 2: No 59 ROMAN URBAN TOPOGRAPHY in Bri
Page 3 and 4: Copyright © 1985 Authors and Counc
Page 5 and 6: Illustrations Fig 1 Miletus Fig 2 C
Page 7 and 8: Introduction: the study of Classica
Page 9 and 10: Introduction and the land divided i
Page 11 and 12: Introduction Fig 3 Timgad: the colo
Page 13 and 14: Introduction Fig 6 Lepcis Magna: th
Page 15 and 16: Introduction xvi
Page 17 and 18: Cunliffe: Aspects of urbanization i
Page 19 and 20: Cunliffe: Aspects of urbanization i
Page 21 and 22: PART II THE PLANNING AND BUILDING O
Page 23: Dilke: Ground survey and measuremen
Page 27 and 28: Dilke: Ground survey and measuremen
Page 29 and 30: The mechanics of the building trade
Page 31 and 32: Ling: The mechanics of the building
Page 43 and 44: Who paid for public buildings in Ro
Page 45 and 46: Duncan--ones: Who paid for public b
Page 47 and 48: Duncan-Jones: Who paid for public b
Page 49 and 50: Civic Pride: a factor in Roman town
Page 51 and 52: Frere: Civic Pride: a factor in Rom
Page 53 and 54: Reece: Roman towns and their plans
Page 55 and 56: Reece: Roman towns and their plans
Page 57 and 58: Wacher: The functions of urban buil
Page 59 and 60: Casey: The Roman housing market leg
Page 61 and 62: Casey: The Roman housing market Evi
Page 63 and 64: Casey: The Roman housing market Rom
Page 65 and 66: Drinkwater: Urbanization in the thr
Page 71 and 72: Forum and Capitolium in the early E
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The quick and the dead: suburbs, ce
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Esmonde Cleary: The quick and the d
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Todd: Forum and Capitolium in the e
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Salway: Geography and the growth of
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Colchester: the mechanics of laying
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Crummy: Colchester: the mechanics o
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New streets for old : the topograph
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Jones: New streets for old: the top
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London in the 1st and early 2nd cen
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Perring: London in the 1st and earl
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Perring: London in the 1st and earl
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Marsden: London in the 3rd and 4th
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Barker: Aspects of the topography o
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Fig 81 Wroxeter: the area of excava
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probably from Viroconium, the robbi
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Forum Iuhi (Cividale) (Italy) 61a f
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