At Athens and elsewhere in the Greek world, the defendant in court was allowed a συνήγορος, literally a “with-speaker,” to collaborate in presenting the case. The Roman term for the advocate in court, patronus, suggests a fundamentally different relation, namely the patronus/cliens model that pervaded Roman society. In early Rome, before advocacy was professionalized, the patronus was expected to exert his auctoritas and force of personality in advocating his client's case before the bar. Continuing as a factor in C.’s time, this element is marked in the oratory of his maturity, when he seeks, on the strength of his long-standing ties to the client, to vouch for him as a worthy citizen and invest him with the aura of his consular auctoritas. The identification of the patronus with his cliens is especially marked in this speech in view of his association with Caelius since he assumed the toga uirilis (§9) and their similar origins as noui homines from Italian municipia; hence he presents Caelius as guaranteed to pursue similar policies for the benefit of the community (§§6a, 77, 80).

Since there was no public prosecutor at Rome, a private citizen had to take upon himself the task of collecting evidence of wrongdoing and filing charges. The would-be prosecutor appeared before the chairman of the relevant quaestio (this might be either a praetor or a iudex quaestionis) and reported the name of the alleged culprit (nomen deferre; corresponding substantive nominis delatio). The official then decided whether to accept the prosecution (nomen recipere) or not; he imposed an oath on the prosecutor to insure that he was acting in good faith. The prosecutor's advantage lay in the fact that only he, and not the defense, could compel the testimony of witnesses; he also had the power to collect relevant documents and place them under seal pending trial. A trial date would be set and a jury empanelled from the album of available jurors established each year by the praetors, whereby each side had the right to reject (reicere) a certain number of proposed jurors. The jury ordinarily consisted of three decuriae of twenty-five each, one decuria of senators, another of equites and a third of tribuni aerarii (a group meeting the same property qualification as the equites); the jurors had to swear to render a conscientious verdict.

It is not easy to construct a coherent prosecution case from C.’s speech since, as usual, he refutes the charges piecemeal and out of order so as to sunder the causal connections argued by the prosecutors. By filing charges de ui the prosecution clearly hoped, however, to forestall Caelius’ (second) prosecution of Bestia de ambitu, since cases of seditious violence received priority (see further on §1 ab eius filio…et uocarit).

In a Roman courtroom it was not discrediting for a prosecutor to admit a personal grudge against a defendant; such an admission could, in fact, be taken as a guarantee of sincerity. Thus the young Atratinus could say that he was prosecuting the man who was hounding his father, Bestia, through the ambitus-court and receive some sympathy and credit for pietas (§1); in all probability he also sought to draw a contrast with Caelius’ treatment of his father, from whose house he had moved out (§3b pater…parum pie tractatus a filio; §18). Herennius Balbus could allege that he was similarly motivated by the plight of his friend Bestia (§56) and stir ill-will against Caelius with a description of his friendly relations with and sudden betrayal of the man (§26).

R. G. Austin's commentary on Pro Caelio introduced several successive generations of anglophone students to the speech and is fondly remembered by many, even those who simultaneously recognize its flaws. Austin deployed his formidable learning on what modern students tend to regard as Cicero's most attractive speech, and he did so in a highly engaging manner. On the other hand, the flaws in his book are also considerable, and time has tended to magnify rather than reduce their scope. Despite his knowledge of Latin grammar, it is possible to contest some of his interpretive and textual decisions. Further, he tended to be gulled by Cicero's rhetorical wiles and too often fell back on his own (often quite deft) renderings at the expense of explaining how the Latin actually works (a need perhaps less urgent in those days). In addition, some decisions taken by author and publisher made the book less than ideally “user-friendly.” It was decided that the Latin text should be a reprint of Clark's OCT, so Austin occasionally found himself in the awkward position of arguing against his own text. In addition, Austin buried a great deal of essential matter in a long series of appendixes that it is difficult to persuade students to read. Finally, over the course of three editions Austin revised some of his views and arrived at new interpretations; these, however, are relegated to a series of “Additional Notes” at the back; in such cases the reader typically first encounters an interpretation that further searching shows to have been repudiated and replaced by a different (and usually better) one. For all these reasons I was not surprised when the series editors asked me to undertake a new commented edition of Pro Caelio in accord with the norms of the Cambridge Greek and Latin Classics.

It is a pleasure to register debts to several benefactors. I thank the series editors and the Syndics of the Press for commissioning the project, The Loeb Classical Library Foundation for generously funding related research expenses, Brent Vine for bibliographic advice, Stephen Oakley and Philip Hardie for reading and improving my drafts and Michael Sharp and his staff for bringing the book to print with their usual care and efficiency; I am solely responsible for any remaining errors. My greatest debt is recorded in the dedication.

The Romans gradually, whether by military action or diplomacy, eroded the power of the successor-states to Alexander's vast empire until they fell under Roman control either by conquest or by testamentary disposition, the latter in the case of the Pergamene kingdom, willed to Rome when Attalus III died without heir in 133, or Cyrene, bequeathed to Rome by Apion in 96. The last to survive were the Ptolemaic kingdoms of Cyprus and Egypt, ruled, after the death in 80 of Alexander II, by Ptolemy XII Auletes and his brother, both sons of Ptolemy IX by an unknown Greek concubine. After much controversy over an alleged will of Alexander II bequeathing his realms to Rome, in early 59, through massive bribery, Auletes was finally able to procure the senate's recognition of his title to the throne and status as “friend and ally” of the Roman people. That did not stop the Romans, however, from acting on another provision of the will of Alexander II by annexing Cyprus (leading to the suicide of Ptolemy of Cyprus) and using the fresh revenue to subsidize the corn dole for the urban plebs.

In Alexandria the annexation of Cyprus and increased taxation required to pay off the monarch's bribes to Roman powerbrokers provoked widespread riots, during which Ptolemy escaped clandestinely and made his way to Rome, where he received hospitality in Pompey's Alban villa and began to lobby for his own restoration. The Romans who had lent money to the king were, of course, in favor in order to protect their investment, but there was disagreement over the commander best suited to the mission, Pompey, Crassus and P. Cornelius Lentulus Spinther (cos. 57) all being candidates. In the meantime word reached Alexandria of Ptolemy's escape and residence in Rome.

The relation of C.’s extant speeches to those he actually delivered in court has been much discussed. The following is a brief survey of the evidence and its implications (the second actio of Verres’ trial, the defense of Milo and the Second Philippic are special cases, the first and third never delivered, the second heavily revised for publication).

C. rarely delivered his speeches from a manuscript, and when he or another speaker did so, the fact might draw comment and/or explanation. Ordinarily he would write out in advance the beginning of the speech and some critical points and have the rest worked out in his mind (Quint. Inst. 10.7.1). Such rough notes for his speeches, the commentarii, remained among his papers at his death and were published by Tiro in at least thirteen books (Diomedes GL I 368.28). Both Asconius and Quintilian were familiar with them but make no mention of any divergence between the commentarii and the delivered speeches (Asc. 87.10 C; Quint. loc. cit. and 4.1.69). The one direct piece of evidence bearing upon the relation of the oral and written versions of the speeches is provided by Cornelius Nepos, who reports that C.’s speech Pro Cornelio was delivered in “almost the same words” as the published version.

The first tribunal de ui at Rome was enacted by the consul Q. Lutatius Catulus in 78 as a tool for suppressing the revolt led by his colleague M. Aemilius Lepidus; it was evidently a quaestio extraordinaria rather than a permanent institution. M. Caelius Rufus was charged under the lex Plautia de ui, which was probably enacted in 70 by the plebeian tribune M. Plautius Silvanus (MRR II 128), the man who also introduced the lex Plautia de reditu Lepidanorum; possibly the lex de ui was a concession to those who feared new unrest if the exiles were allowed to return. Certainly the lex Plautia de ui was in effect by 63, since in that year Catiline was prosecuted under it (TLRR 223). Perhaps Plautius proposed this legislation, rather than rely on the existing quaestio maiestatis, since the latter was better adapted to prosecuting the ringleaders of armed violence than the rank and file. The lex Plautia outlawed any act of violence that was directed contra rem publicam and established a standing court (quaestio perpetua) to hear relevant charges; it also provided that that court meet daily, even during festivals (dies festi), and that its cases receive priority over other pending trials.

This is not the place for a full biography of Clodia Metelli, but since C. presents her as his main antagonist in this speech, it is worth considering briefly who she was and what rôle she played in this trial. A daughter of Ap. Claudius Pulcher (cos. 79), she was probably born by 93; she was married, possibly by 79, to Q. Metellus Celer (cos. 60). Of her three brothers, Appius achieved the consulate (54), Gaius the praetorship (56), Publius the tribunate of the plebs (58) and aedileship (56). She also had two sisters, though the order of their births is unclear. In any case, both of her sisters also married consuls: one married L. Licinius Lucullus (cos. 74); the other, Claudia Tertia, married Q. Marcius Rex (cos. 68). Clodia herself was widowed by the sudden death of her husband in 59 (see further on §§59–60). She is known to have possessed three properties, a house on the Palatine, gardens on the Tiber and a house at Baiae. There is no reference to her dated later than 44.

The date of publication of Cael. has been controversial since Norden argued that it remained unpublished during C.’s lifetime because the Council of Luca of mid-April interfered with any plans for publication; hence it was edited posthumously from his papers with “doublets” remaining in the text as traces of C.’s improvisation during delivery. But the “doublets,” i.e. reprise of topics previously mooted (§28 ∼ §§41–3 and §38 and §§48–50), can be otherwise explained; and C. heard of the Council of Luca only ca. 25 April; even if he drew immediate conclusions from that information, in view of the speed with which he could work, the prior writing up and circulation of the speech is not excluded. As a general rule it is probably true that C. wrote up and circulated quickly the forensic speeches that he meant to publish. Crawford points out that a desire to memorialize “the devastating attack on the Clodii” would have argued for immediate publication; indeed the speech shows the wounds of the exile still raw (§§32, 50).

So far, we have concentrated on developing a method for modeling fluids. We established the idea of the continuum to allow us to describe flows with continuous functions, and we introduced the use of the control volume (CV) to free us from having to follow individual fluid particles (see Chapter 3). We described a method of accounting for stresses in fluids (see Chapter 4) and showed how stress and motion are related through the constitutive equation (see Chapter 5). We developed a solution methodology that led to the microscopic balance equations and, finally, to solutions of simple flow problems (see Chapter 6). We have all of the tools necessary to solve flow problems, and we now turn to the task of modeling and understanding the flow behaviors described in Chapter 2.

In this chapter, we concentrate on internal flows, which are flows through closed conduits. Chapter 8 discusses both external flows, in which fluid moves over or around obstacles, and an important class of flows called boundary-layer flows.

In this chapter and in Chapter 8, we address complex, realistic, and practical flow problems with our modeling methods. We begin the analysis of complex problems with a microscopic analysis on an idealized system.

Our task is to learn to model flows. To set up the models, we draw on our intuition of how fluids behave; for example, we often can guess the direction that a flow takes under the influence of particular forces. Intuition also may enable us to identify symmetries in a flow field. Intuition comes from experience, however, and for introductory students, experience may be in short supply.

One solution to a lack of experience is to experiment with fluids. Unfortunately, not all of us have access to pumps, flow meters, and piping systems; therefore, it is worthwhile to take a laboratory course in fluid mechanics, if possible. Another way to build experience with fluid behavior is to view flow-visualization videos. Between 1961 and 1969, a group of experts in fluid mechanics (the National Committee for Fluid Mechanics Films [NCFMF]) produced a series of flow- demonstration films [112] that introduce fluid behavior; the films and film notes are now available on the Internet. There also are books [170] and other media [65] that catalog fluid behavior, as well as Web sites on which researchers have posted flow-visualization videos, including the Gallery of Fluid Motion [133], and elsewhere [182]. These sites bring to life all types of fluid behavior, from the mundane to the esoteric.