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Length-units in Roman Town Planning: The Pes Monetalis and the Pes Drusianus

Published online by Cambridge University Press:  09 November 2011

R. P. Duncan-Jones
R. P. Duncan-Jones
Affiliation:
Gonville and Caius College, Cambridge
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Extract

The careful grid-patterns which are such a characteristic feature of Roman towns and camps are one of the most vivid illustrations of the Roman capacity for efficient organization. It is obviously interesting to know what units of size were used. The clearest demonstrations of the units employed in land-measurement occur in centuriation. As its name indicates, centuriation was the division of land into centuriae, squares measuring one centuria in area. Their side was 2,400 Roman feet. Considering the distances involved, the surviving evidence shows remarkable accuracy: centuriae that can still be measured range from 711 m in Emilia to 703 m in the Chott el Djerid, a variation of ±0·6 per cent. Shorter measuring units listed by Roman metrological writers are the actus of 120 feet, the pertica or decempeda of 10 feet, and the passus of 5 feet.

Type
Articles
Information
Britannia , Volume 11 , November 1980 , pp. 127 - 133
Copyright
Copyright © R. P. Duncan-Jones 1980. Exclusive Licence to Publish: The Society for the Promotion of Roman Studies

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References

1 F. Castagnoli, Le ricerche sui resti della centuriazione (1958), 22.

2 Hultsch, , MSR ii, Latin index s.v.Google Scholar

3 Hultsch assessed the pes monetalis as 0·2957 m. But extant measures vary at least within the range 0·291—0·297 m, and there is little purpose in hoping for an accuracy of more than three significant figures (J. Hultsch, Griechische und römische Metrologie2 (1882), 98; cf. G. C. Boon, Silchester (1974), 97 and 293).

4 The reference to the pes Drusianus reads ‘item dicitur in Germania in Tungris pes Drusianus, qui habet monetalem pedem et sescunciam’. (Hyginus de condicionibus agrorum (Lachmann), 123. 9–10.) If the standard foot, the pes monetalis was 0296 m (n. 3), the pes Drusianus, being 1/8 larger, would measure 0333 m. Frere and Walthew interpret the pes monetalis as 0296 m, as here, but the pes Drusianus as 0332 m. That value has been adopted below in TABLE II in order to obtain correct metric equivalences from the measurements in Drusian feet given by Frere. But in all other cases, the pes Drusianus is here regarded as 0·333 m.

5 See n. 3.

6 The dimensions are 35·28 × 141·12 m. This exactly equals 120 × 480 feet if the foot used there was 0·294 m, Davin, P., Revue tunisienne n.s. i (1930), 73–85Google Scholar, at 83; cf. Humphrey, J. H. (ed.), Excavations at Carthage 1975 conducted by the University of Michigan i (Tunis, 1976), 17–19.Google Scholar

7 A. Piganiol, Les documents cadastraux de la colonie romaine d'Orange (1963), 331–3.

8 Frere 1977, 92.

9 See n. 6.

10 F. Haverfield, Ancient town planning (1913), 101 (35 × 180 m).

11 Walthew 1978, 336–41. The isolated dimensions at Silchester cited tentatively by Walthew (ibid.) do not seem enough to overturn Boon's contention that the standard actus was not known at that town (Boon (n. 3), 96).

12 E. Boeswillwald, R. Cagnat, A. Ballu, Timgad(1905), 346–7. The square insulae range from 21·8×21·3 to 20·65 × 20·45 m, representing extremes of 73·6 and 69·1 Roman feet. The rectangles measure 28·65 × 20·8 and 28·25 × 20·8 m.

13 F. Castagnoli, Orthogonal town-planning in antiquity (1971), 108; no : units at Florentia and Libarna measure 60×60 1×1=202·7×202·7 Roman feet. Haverfield, op. cit. (n. 10), 123: Augustodunum, 98×98 yards = 302·7 × 302·7 Roman feet.

14 Castagnoli (n. 13) 104 (bis); Haverfield (n. 10) 88; Castagnoli 104 (bis); 106. Rendered into Roman feet of 0·296 m, the dimensions (which are usually approximate) are as follows: Aquileia 209·5 × 280·4, Placentia 270·3×270·3, Turin 247·1 × 370·7, Ariminum 250×371·6, Bononia 270·3×384, Parma 152×185·8.

15 cf. n. 3 and n. 6.

16 Boon (n. 3) 96–7. Here the Drusian foot is regarded as 1⅛ of the Roman foot of 0·296 m, therefore 0·333 m (see n. 4 above). Boon takes it that the Drusian foot is 1/120 of the insula IV module of 39·83 m, or 0·3319.

17 Walthew 1978, 343; Frere, S. S., Verulamium Excavations i (1972), fig. 8.Google Scholar

18 cf. Hultsch, MSR ii, xxv–xxviii.Google Scholar An ancient discussion is that by Volusius Maecianus, ibid. 61 ff.

19 cf. n. 2 above. Isidore mentions the possibility of perticae of 10, 12, 15 and 17 feet. But these depended on the fertility of the soil (they were evidently fixed units of crop-yield), and seem to belong to a different context from that of town-planning (Hultsch, MSR ii. 136. 1–8).Google Scholar

20 Walthew 1978, 343, n. 60.

21 cf. n. 7.

22 Walthew 1978, 343–4; Frere (see n. 17) fig. 10.

23 Walthew also cites evidence for the pes Drusianus from Augusta Raurica (346–7 and 345 fig. 2). For a different interpretation of the units there, see J. Ewald in E. Schmid, L. Burger, P. Biirgin (ed.), Provincialia (1968), 80 ff. To the present writer, the archaeological evidence from this town seems too slight for metrological conclusions.

24 Frere 1977, 93, fig. 3; 94, fig. 4.

25 Frere 1977, 93.

26 There is a simple reason for this limitation. The distance of any whole number value in Drusian feet from the nearest whole number value in standard feet cannot be more than half a standard foot (14·8 cm). The margin of error that will allow one of these to be distinguished from the other cannot be more than half this distance (7·4 cm), and in any normal distribution it will usually be less (see e.g. TABLE II, column V). Therefore a permitted margin of error of 75 cm in observations intended to establish the presence of the Drusian foot must be too high.

27 For the actual measurement, Frere, S. S., Joseph, J. K. St, Britannia v (1974), 33.Google Scholar

28 For measurements, see ibid. 32 and 30.

29 Frere, S. S., Joseph, J. K. St, Britannia iv (1973), 288.Google Scholar

30 The dimensions of the possible praetorium at Baginton which Walthew interprets as 40 x 30 m appear so uncertain and so irregular from the plan that they cannot safely be used for metrological inference. For the building, see Wilson, D. R., Britannia v (1974), 431 and fig. 10.Google Scholar

31 W. Glasbergen, W. Groenman-Van Waateringe, The pre-Flavian garrisons of Valkenburg Z.H. (1974), 22.

32 Duncan-Jones, R. P., Zeitschr.f. Pap. u. Epig. xxi (1976), 43–62.Google Scholar There were at least five capacity measures called ‘modius’. Italic (A) was about 862 litres (p. 52); Italic (B) about 10–53 (pp. 59–61); castrensis (A) was about 11·64·11 85 (pp. 45, 59), and castrensis (B) about 1293 (p. 59). There was at least one further standard, 2/9 larger than castrensis (B) (p. 60). A newly published measure marked SEX(tarius) ITAL(icus) seems to belong to Italic (B): its original capacity was 0·645 1, or slightly more. Another new SEX(tarius) measure, holding 0·818 1, evidently belongs to castrensis (B) (cf. Gabričević, M., Arch. lug. xv [1977], 42–4).Google Scholar