Time for the Ancients

Front matter

DE GRUYTER

P. N. Singer Time for the Ancients

CHRONOI

Preface

This book explores ancient Graeco-Roman attitudes to time, its perception, measurement and daily management, and does so with a particular focus on medical approaches and medical sources.

I aim to address such questions as: How did people in the Graeco-Roman world divide organize or divide their days? How did they understand the aging process, or the successive phases of their lives? What was the significance of the changes in the seasons to their daily regimes? What was the relevance of these and other ‘cycles’ to the understanding of health and disease? What was the role of measurement, and of various technologies of measurement, in these contexts? How did they conceive of their own lives within a broader time span, in relation to — real or imagined — previous ages?

There has been much recent work on time in the ancient world, which has focussed on a number of different topics, especially: calendars and techniques of time measurement; socio-cultural constructions of the lived day, and of different ages or stages of life; attitudes to the past; philosophical speculations, definitions and analyses.’ But these areas of study have remained to a large extent separate; there is no introductory study offering an overview taking account of them all.

This book aims to fill that gap. At the same time, and while exploring the above questions and offering a synoptic account on the basis of a wide range of sources, it has a particular focus medical writing, and an even more particular one on the work of Galen.

Let me offer a few words by way of explanation of the rationale, first for the focus on medical sources, and secondly for the especial focus on Galen.

Medical writing and medical conceptions constitute a major source of evidence for ancient approaches to and experiences of time, as well as its division and measurement, and the context of this evidence is one of major salience for everyday lives. Medical texts pay closer attention to time than any other literary

1 On time measurement and calendars, as well as on the social and political significance of the latter, see for example: Riipke (1995), (2011); Schaldach (2001); Hannah (2005), (2008), (2009), (2020); Lehoux (2007); Wolkenhauer (2011); Winter (2013); Bonnin (2015); GraShoff et al. (2015); Ben-Dov and Doering (2017); Talbert (2017); Bultrighini (2018), (2021a), (2021b); Jones (2020); on daily lives: Ker (2020); Wolkenhauer (2020); on stages of life: Wiedemann (1989); Kleijwegt (1991); Parkin (1999); Laurence (2000); Harlow and Laurence (2002); Scheidel (2001); Cokayne (2003); on attitudes to the past: Csapo and Miller (1998); Darbo-Peschanski (2000); Falkner (1990); Goldhill (2001); de Jong and Niinlist (2007); Richter and Johnson (2017); on philosophical theories: Sorabji (1983) and, on Aristotle, Coope (2005).

Vill —— Preface sources, on at least three temporal levels: that of precise times within the day (in the context of both health prescriptions and diagnostic observation); that of the seasons of the year (in the context of their relative impact upon health); and that of the human life cycle, from infancy to old age, understood in biological terms. They are thus a very rich — but also a comparatively neglected — source for both theoretical speculation and technological innovation regarding time, and for its experience and management in the ancient world. Amongst other things, they help us to chronicle the growing importance of numbered hours in the Graeco-Roman world and, relatedly, the possible relevance of the growing use of time-telling technologies for everyday time management. A clearer understanding of these developments must at least provide some corrective to the historiographical view which still enjoys considerable currency, that precise time measurement only became important in the conditioning and structuring of everyday lives from the early modern period — still more so to the view that it only achieved real social significance as a function of the modern industrialized workplace.”

Moreover, medical texts relating to time offer a distinctive perspective not found in other texts. This is partly a function of the highly contingent, personalized, observation-based, even anecdotal nature of much of the material, which vividly highlights - for example — aspects of individual exercise regimes, diets, sleep patterns and recurrent ailments; details of the daily care of infants or children; or individual experiences and perceptions of the aging process. But the perspective is distinctive in another way too. The medical discourse in some respects offers an alternative model, even a counterblast, to those discourses or traditions which privilege a sacred, social or political calendar. The ambition of medical theory and practice, by contrast, is tendentially to abolish all artificial (or god-given) distinctions between periods of time, acknowledging only those with a biological, environmental or cosmic basis. Thus, while much important recent scholarly work has focused on the calendar, and on the notion of ‘festive time’, medical perspectives may provide a corrective, or at least a countervailing set of views and experiences. Against a history which tends to privilege tradition and ritual practice, medical sources suggest a view of human experience and human behaviour where differences from one hour, day or month to the next are understood in terms purely of seasonal and biological changes, of environment, diet and daily activity.

2 The point is made strongly by Miller (forthcoming), who mentions as classic statements of such views Thompson (1967); Landes (1983); and, in a similar vein Jenzen and Glasemann (1989); Dohrn-van Rossum (1996).

Preface —— IX

The rationale for the focus on the second-century-CE doctor and philosopher Galen is partly covered by the above considerations; but it is also the case that his writings happen to include a range of discussions which, taken together, in themselves offer a significant overview of ancient attitudes to time, both within and beyond the medical context. Let me give a brief account of four examples of the unique value of the Galenic material. First, Galen gives the fullest account extant in a literary source of the construction of a sundial, and also of the relationship between sundials and water-clocks. Secondly, he offers by far the richest material for ancient conceptions of different ages, or times of life, and their medical and lifestyle implications. Thirdly, he gives by far the fullest account in our sources of the nature of diagnostic and clinical practice, and how this relates to close temporal observation. Fourthly — and in a more theoretical vein — he presents an original account of our perception of time in relation to motion, and relatedly also of speed and rhythm, which both draws both on existing philosophical accounts and theoretical conceptions and on his clinical experience. This latter discussion — in conjunction with evidence from other medical sources — illuminates ancient views of the extent and limitations of human perception, of the role of quantification, and of rhythm, in both clinical and everyday contexts.

The choice of texts, and the main temporal focus on the second century CE, are partly determined also by considerations of the nature and interrelationship of our surviving sources; and these considerations should be mentioned here too, as they may help to explain what may otherwise seem an unbalanced or eccentric chronological approach. The overwhelming majority of medical sources from the Graeco-Roman world belongs to one of two groups: the so-called ‘Hippocratic corpus’ on the one hand and the (far more voluminous) works of Galen on the other. The former texts, though spanning a range of dates and authors, were mainly written somewhere in the Greek-speaking world in the fourth or late fifth century BCE,’ the latter mainly in the second half of the second century CE at Rome. There is a gap of several centuries between these two textual islands, from which period we have very few independently surviving texts, often themselves of uncertain date. Moreover, much of what we do know of the medical authors or developments between these two periods — for example, of the important Hellenistic doctors Herophilus and Erasistratus — is from the testimony either of Galen or of authors of even later periods. Galen thus looms very large in our ancient medical evidence, both as an author in his own right and as a source for earlier developments. Moreover (as we shall see especially

3 On the problems of the ‘Hippocratic corpus’ see below, p. 36 with n. 3.

X — Preface in chapter 3), his works have a close theoretical and ideological relationship with those of the earlier periods, with certain of the ‘Hippocratic’ works in particular.

For all these reasons, it is difficult to tell anything like a diachronic story of developments in any area related to medical history. I have chosen rather — partly because of this consideration and partly as a function of my own research interests, which have focussed more closely on Galen — to paint a synchronic picture, based mainly in second-century Rome, but at the same time to contextualize this picture with the help of various other texts, some from much earlier periods, but all informing the same intellectual and experiential tradition. In the process, there is inevitably some jumping backwards and forwards, for example between Galen and ‘Hippocrates’, but it is hoped that such leaps are informative and enriching of that central synchronic picture.

The book thus offers at once a synoptic view of the current state of knowledge of Graeco-Roman thought and practice, in such areas as time measurement and management, approaches to aging, and the perception of time in relation to motion, and also the results of my own and others’ latest researches in the specific field of ancient medicine, for example in relation to disease diagnosis or to health prescriptions, which substantially enrich our understanding of these questions.

I should mention a few areas that I do not attempt to address, even synoptically. I give no account here of the relationship of festive to everyday time, or of the extent to which the festive calendar conditioned perceptions of or management of time. The role of both political and religious calendars, and the dedicating of days within the calendar to specific purposes (festive, commercial, juridical, etc.), as well as the related development of a division into either seven-day weeks or eight-day nundinae, constitutes a hugely important aspect of the ancient experience and management of time, which has received a comparatively high level of attention in recent literature.‘ These areas have been beyond my scope; moreover, as already suggested, the medical discourse in some ways offers a countervailing historiographical perspective.

Nor, while examining a number of other crucial cycles, do I consider conceptions of cycles of years, arising in either a religious or a philosophical context.’ Such consideration of the measurement of longer periods of time would poten-

4 See especially Hannah (2005), chapters 3 and 5; Riipke (1995); for further perspectives Beard (1987) and, on the development of the weekly time division in Roman imperial and later times, Bultrighini (2018), (2021a), (2021b).

5 On the ancient Jewish concept of the Sabbatical year, for example, see Carmichael (1999); Casperson (2003); and, for later ramifications, Krinis (2016). Cyclical philosophical notions, meanwhile, would prominently include the Stoic theory of the periodic conflagration of the universe.

Preface —— XI tially lead also to analysis of the complex history of the development of the solar calendar and its division into months, and relatedly of the relationship of solar and lunar calendars — again questions not addressed here.°

There is much recent work, both within classical studies and within social anthropology, which approaches the question of attitudes to and experience of time from a range of anthropologically-informed theoretical perspectives.’ The present study does not aim to engage with such theoretical approaches headon, let alone to advance a new theoretical framework of its own; it does, however, seek to take account of discussions arising in such work where they seem of particular relevance to the specific topics under investigation.

The book is structured in five chapters, each of which takes one large thematic area and aims to consider it from both a broader textual or social perspective and in relation to a more narrowly medical (or in some cases Galenic) perspective. In the first chapter I consider the ‘horological scene’ of imperial Rome, the importance and the varieties of time measurement and management in daily life, and in particular the division into hours, on the basis of a wide range of sources. This broadly-based account is then followed by a more detailed investigation of the Galenic evidence, both for daily health prescriptions and for the role (and interrelationship) of sundials and water-clocks. In the second chapter, I consider two closely related ‘cycles’, that of the human lifespan and that of seasons, and the ways that these were conceptualized, experienced or negotiated, both in Graeco-Roman societies more generally and in the medical — especially Hippocratic and Galenic — discourse in particular. Thirdly, and with a main focus on Galen, I consider the two related questions of the (self-)perception or construction of a life or personal biography in the ancient intellectual world and of the attitude to, and nascent periodization of, the past. The fourth chapter investigates the importance of both day and time divisions in ancient diagnostic and clinical practice; it focuses on the crucial medical concepts of krisis and kairos, also attempting to place these in a broader intellectual and literary context. Finally, I examine Galen’s theoretical-philosophical contribution to the discussion of time, both placing this in the broader Greek philosophical tradition and considering its relevance to important clinical and practical questions, in

6 See again Hannah (2005), chapter 3, for an intricate account of Greek solutions to the problem, how to divide the year into a regular number of regular months, and of the related question of calculation of dates for periodic festivals such as the Olympics; ibid., chapter 5 for similar issues in Roman calendar-making.

7 Prominent contributions in the former category include van Groningen (1953); de Romilly (1968); Loraux (1986); Bettini (1991); Csapo and Miller (1998); Darbo-Peschanksi (2000); Rosen (2004); in the latter, Good (1968); Gell (1992); Turetzky (1998).

XII —— Preface particular the nature of our assessment of time, speed or motion, and the role of qualitative and quantitative elements in this.

As a function of this particular thematic approach, my focus in the book is neither entirely on ‘long’ nor on ‘short’ time, to use the terminology adopted in recent literature. While most of the present study is related to a variety of ‘short’ time units — from hour divisions down to the microscopic divisions theoretically involved in the measurement of the speed of the pulse — I also explore the measurement and conception of time in two ‘longer’ contexts, that of the ages or phases of life, and that of attitudes to and self-positioning in relation to the past. Moreover, the thematic organization just outlined entails that I do not move neatly either from shorter to longer time units or vice versa, as the various units arise in different ways in relation to the themes successively addressed.

Through its particular focus, the book aims to open a window into some of the most significant questions regarding the ancient awareness, measurement, management, perception and conceptualization of time, and the salience of these to both medical theory and practice and everyday experience.

8 See especially the essential work of Miller and Symons (2020).

Contents List of Illustrations — XV List of Tables — XVII

Chapter One: Time measurement, time management: days, hours and routines — 1 Introductory: modes of time measurement at Rome — 1 Meridian lines and sundials; seasonal hours — 4 Horai (Õpaı): from seasons to hours — 6 Sundials in the Graeco-Roman world — 8 Water-clocks —— 13 Accuracy —— 17 Time perception, time management and the use of time-telling devices — 24 Medical texts and practices concerning time management —— 27 Galen against ‘festive time’ — 33

Chapter Two: Times of life and times of year: the ever-shifting cycles — 35 Introductory — 35 The cycle of life: the ages of man (and woman) in the Graeco-Roman world — 36 Medical authors on the life stages — 43 The yearly cycle: the seasons —— 51 Non-periodic disease recurrence: some endless cycles — 61 Conclusion regarding medical discussions of cycles — 63 A final consideration: temporal and atemporal human beings — 64

Chapter Three: Lives in time: history, biography, bibliography —— 67 The old and the new — 72 Galen on the old and the new (1): the ideology of the ancient — 74 Galen on the old and the new (2): historiography and periodization — 83 Galen on his own age — 89 Galen on his own life and works — 91 A parallel biography: Porphyry’s Life of Plotinus — 98

Chapter Four: Time for the doctor: crises, perils and opportunities — 102 Kairos, krisis and peira: a perilous time —— 102

XIV —— Contents

Periodic diseases —— 106

Fevers and their recurrence: Hippocrates; Galen; Galen’s rivals — 108 Non-Galenic views: over-simplification and over-complication —— 109 Galen’s own schemes —— 116

Reconciling theory, observation and authority: Galen’s medical

month —— 117

Chapter Five: Time, motion, rhythm: reality, perception and quantification — 123 Philosophical questions and the relationship of time to motion — 124 Galen on time (1): evidence for his theoretical analysis — 128 Galen on time (2): further analysis and justification — 132 Galen on speed: the measurement of the pulse — 136 Minimal units of time (4): the atomic nature of time perception — 148 Minimal units of time (2): the analysis of rhythm —— 152 Summary on minimal time units in Aristoxenus, Herophilus and Galen — 158 An isolated case of quantification? Pulse rate and the water-clock —— 159 Conclusion — 162

Bibliography — 165 Primary Texts — 165 Citation conventions and abbreviations — 165 List of primary sources cited — 166 Secondary Literature — 170

Index of names — 181

General index — 184

List of Illustrations

Figure 1 The horologium Augusti as depicted on the base of the Column of Antoninus Pius in Rome

Figure 2 The three great Augustan monuments — mausoleum, Ara Pacis and horologium - in the northern Campus Martius in Rome

Figure 3 Some examples of sundials in the Graeco-Roman world

Figure 4 An Egyptian outflow water-clock

Figure 5 Ctesibius’ sophisticated water-clock

Figure 6 Diagram of Galen’s account of the design of a water-clock

Figure 7 The two-sphere model of the cosmos, with the zodiac and planets

Figure 8 The heliacal rising of the Pleiades, Hyades and Orion

Figure 9 ‘Mundus homo annus’: the mediaeval circle of correspondences of elements, seasons, fluids and ages

Figure 10 A Roman funerary inscription recording a lifespan in years, months, days and hours

Figure 11 Kairos personified as a dashing youth, with a knife and scales

Figure 12 The bedside as battlefield: Galen correctly diagnosing the illness of the emperor Marcus Aurelius, surrounded by rival physicians.

Figure 13 Calculating the period (wrongly): Galen’s conversion table in Periods

Figure 14 The fine-tuning of the senses (1): tuning a lyre

Figure 15 The fine-tuning of the senses (2): the hands and the pulse

38 OpenAccess. © 2022 Singer, published by De Gruyter. This work is licensed under the

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List of Tables

Table 1 Ages in the ‘Hippocratic’ Hebdomads

Table 2 A standard ‘Hippocratic’ age division (from Regimen 1.33) Table 3 The stages of life in Galen

Table 4 Divisions of the seasons (according to Regimen)

Table 5 Galen’s typology of fevers

Table 6 The mediaeval circle of correspondences: ‘world — man - year’ Table 7 Galen’s periodization of the past

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Chapter One: Time measurement, time management: days, hours and routines

In this chapter I explore Graeco-Roman techniques of, and attitudes towards, time measurement, from the twin perspectives of everyday life and medicine. I survey literary and archaeological evidence for the two main available technologies of time measurement, sundials and water-clocks, and consider what this evidence tells us about their differential accessibility and context of use, and about Roman attitudes to daily or hourly time organization. I then proceed to examine further some literary, and, in more detail, some medical texts which shed light on ancient attitudes to time management and the division of the day; on the importance of, and relationship between, the two forms of time measurement, as well as the relationship of seasonal to equinoctial hours; and on the balance of work and leisure, in particular exercise, activities within such daily time divisions.

Introductory: modes of time measurement at Rome

An obelisk towered high over the Campus Martius in Rome. Built in 10/9 BCE, the horologium of the emperor Augustus cast its shadow over a long stretch of the low-lying area, where a metal line and markings had been laid in the ground. It was itself visible from a great distance and complemented two other great Augustan edifices in the same area: the Mausoleum Augusti and the Ara Pacis. (See figures 1 and 2.) The line on the ground ran due north from the obelisk: a meridian, which the shadow hit at noon each day. The markings along its length indicated different dates, and these would be hit by the shadow at noon on successive days, as it grew longer or shorter in the course of the year.

Prominently placed above the forum, meanwhile — the centre of both legal and commercial activity in the city — were one or two sundials, visibly dividing the passing time of daylight into twelve equal units, which, by the late second century CE, the date of the texts which we shall focus on in this chapter, had stood there for more than three hundred years. Other, equally publicly visible, sundials were features of cities throughout the Graeco-Roman world.’

1 For detail and for an account of the early Roman history of time measurement, and for the historical sequence of publicly accessible markers of time in the city, see Wolkenhauer

38 OpenAccess. © 2022 Singer, published by De Gruyter. This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License. https: //doi.org/10.1515/9783110752397-004

2 — Chapter One: Time measurement, time management: days, hours and routines

Figure 1: The horologium Augusti as depicted on the base of the Column of Antoninus Pius in Rome. An obelisk emerges from the lap of the personified Campus Martius; a winged figure, possibly Eternity (Aiðn) conducts Antoninus and Faustina to the heavens. The column base is now in the Vatican Museums. Image: https://commons.wikimedia.org/wiki/File:Musei_vatica ni_-_base_colonna_antonina_01106.JPG

A few steps from those public sundials, the ancient visitor to the forum — if by chance business affairs took him into the Basilica Aemilia et Fulvia - would find an equally venerable instrument of time measurement, a water-clock or clepsydra, placed there in the year 159 BCE, and dividing the day into (probably) half hours.

Water-clocks, indeed, had the capacity to measure much smaller units of time than that. The main attested use of the clepsydra was, as we shall see, in legal contexts; but here the water-clocks in question were simple outflow devices, whose sole function was the demarcation of short, distinct blocks of time. At the other end of the technological spectrum, an elaborate and sophisticated clepsydra might constitute a luxury object or perhaps status symbol, for example

(2020), esp. 218-20. The main literary source is Pliny, Natural History 7.60.212-15. The Twelve Tables made reference only to the moments of sunrise and sunset, which were publicly displayed on the Rostra; the public announcement of noon was a somewhat later innovation; and Pliny records accounts of a first sundial erected either at the Temple of Quirinus, eleven years before the Pyrrhic War (i.e. c. 295 BCE), or at the Rostra during the First Punic War (c. 262 BCE). He adds that this sundial was obeyed for many years although inaccurate, and a new one was erected c. 164 BCE. See also Hannah (2009): 134-6, and further note 12 below.

Introductory: modes of time measurement at Rome —— 3

1. Original position of obelisk (after Schütz}

2. Ara Pacis

3. Mausoleum of Augustus

4. Excavation of meridian line

5. Unsuccessful excavation

6. Find-spot of cippi

7. Borehole number 13

10. Arco di Portogallo

11, Present-day site of obelisk with meridian 12. Extent of Buchner’s original reconstruction 13, Extent of Buchner’s circular reconstruction

„ọ Piazza del & Parlamento = = S k S

Piazza Piazza di Colonna Montecitorio l 5, a

Figure 2: The three great Augustan monuments - mausoleum, Ara Pacis and horologium — in the northern Campus Martius in Rome. The plan, showing the monuments in their positions on a map of the modern city, also indicates their ancient prominence and interrelationship. Note that nos. 12 and 13 show the dubious reconstructions of the monument as a sundial, by Buchner, while no. 4 shows its actual function as a meridian line. The image is reproduced by kind permission of Peter Heslin from his article (2007).

in the dining room of a well-to-do citizen, whose guests might pass a little time admiring the ingenuity and luxury of their host’s most up-to-date acquisition.’ Such a water-clock might be capable of measuring hours and even subdivisions

2 Petronius describes a rich man boasting of his water-clock (Satyricon 26); cf. Pliny, Letters 3.1.8.

4 — Chapter One: Time measurement, time management: days, hours and routines of hours, of both day and night, throughout the year, with impressive accuracy. Some water-clocks were also on prominent display, certainly by the second century CE, in a number of public spaces — for example at gymnasia, theatres or sanctuaries — although little is known of their technological specifications or measuring capabilities.” There is also evidence of the use, again in the private context, of handheld or portable sundials. These again would be objects for the elite, probably not of great practical value and certainly not in widespread use. Archaeological evidence suggests that both handheld sundials and sophisticated water-clocks were a rarity.’

These few examples present us with a way into the world of ancient time awareness and time management. We have moved, in this brief overview, from the most publicly accessible forms of time measurement in Rome — which were at the same times the ones dealing in the largest units, marking the position of the day within the year, the moment of midday or, at the smallest level, the division the day into hours — through those used in business and legal contexts, in which it was important to have a conception and a measurement of smaller units, to the level of the private, elite household, in which more accurate devices might have been rather a diversion than something of serious practical value.

We shall proceed to consider in more detail the physical construction, context and use of these different technologies, and what these — and some relevant texts — tell us about ancient attitudes to time management, daily organization, leisure and punctuality.

Meridian lines and sundials; seasonal hours

The spectacularly public monument with which we began functioned both as a calendar, showing the moment of the year that had been reached, and as a daily indicator of noon. The information laid out on the ground for the first of these purposes — the marks along the meridian line’s length — included such labels as ‘beginning of spring’ and ‘Etesian winds’ (whose arrival early in the summer was a well-known marker of the beginning of the safe sailing season), as well as the names of the zodiac signs and a mark for each degree of the zodiac. On its progress from its shortest extent, at the summer solstice, to its longest, at the winter solstice, the shadow came level with a series of markings on one side

3 See further p. 24 with n. 31 below. 4 See Talbert (2017); Jones (2020): 125.

Meridian lines and sundials; seasonal hours —— 5 of the line, where letters are to be found mentioning the zodiac signs of the late summer to winter months, as well as others corresponding to specific moments in that half of the year; as the shadow shortened on successive days between December and June, the corresponding markings were to be read on the other side of the line.

The utility of such a meridian line, then, is twofold. Passers-by would be made aware of the approach and passing of midday, although of no smaller division of the day than that; but this in itself may have assisted in the regulation and organization of their day. But the observer of the shadow at midday would also gain a confirmation of the position within the calendar on any given day. One chief aim of the construction may indeed have been to give reassurance of stability, to make an assertion of the new era or reliability of the calendar that was to result from Augustus’ taking of control over the calendar after a period of drift and uncertainty. The reliability of the new system, after Augustus’ reforms and adjustments, would be manifest from the agreement of the lines visibly marked on the ground with the days and festivals of the civic calendar. Indeed, the purpose of the instrument was at least as much to impress and dominate as it was to inform; there was, as a number of scholars have pointed out, a clear political message to be read, not just in the horologium’s visibility from afar, but also in its proximity to and physical relationship with the other two great Augustan monuments in the area, mentioned above.’

We might say, then, that the horologium Augusti is both misnamed and a somewhat unusual case: not in fact a sundial, not a ‘teller of the hours’, but

5 See especially Heslin (2007) and (2019), emphasizing both the ideological or propaganda function of the meridian - giving visible form to Augustus’ reform and stabilization of the calendar, and mutually reinforcing the other two major Augustan monuments in the northern area of the Campus Martius — and its role in ‘making Rome run on time’. Augustus had taken control of the calendar on his adoption of the role of pontifex maximus on the death of Lepidus the previous year, and had instituted adjustments that had become necessary as a result of an inaccurate intercalation of leap days (three instead of four) in leap years in the time of Julius Caesar, and a failure to address this for more than thirty years. Heslin, following Schiitz, rejects the role previously attributed to the horologium, especially by Buchner, as a sundial, with a large physical presence on the ground of the Campus Martius. (A further controversial aspect, explored especially by Heslin 2019, is the probable re-laying of the meridian - and appropriation of the ideological message of the monument - by the emperor Domitian, nearly a century later.) While the controversy has continued, a broad consensus now favours the view of the horologium as a meridian line and not a sundial. Important further discussions of the role and significance of the monument are given by Zanker (1988); Barton (1995); Rehak (2006); Hannah (2011); the controversy, and history of the archaeological excavations, is summarized both by Heslin and by Haselberger (2011), (2014). On the public aspect of calendars more generally see Riipke (1995), (2011).