§419. Uses of the Ablative As Instrumental

A noun or pronoun, with a participle in agreement, may be put in the Ablative to define the time or circumstances of an action. This construction is called the Ablative Absolute:—¹

• Caesar, acceptīs litterīs, nūntium mittit (B. G. 5.46), having received the letter, Cæsar sends a messenger (the letter having been received).
• quibus rēbus cōgnitīs Caesar apud mīlitēs cōntiōnātur (B. C. 1.7), having learned this, Cæsar makes a speech to the soldiers.
• fugātō omnī equitātū (B. G. 7.68), all the cavalry being put to flight.
• interfectō Indūtiomārō (id. 6.2), upon the death of Indutiomarus.
• nōndum hieme cōnfectā in fīnīs Nerviōrum contendit (id. 6.3), though the winter was not yet over, he hastened into the territory of the Nervii.
• compressī [sunt] cōnātūs nūllō tumultū pūblicē concitātō (Cat. 1.11), the attempts were put down without exciting any general alarm.
• nē vōbīs quidem omnibus rē etiam tum probātā (id. 2.4), since at that time the facts were not yet proved even to all of you.

a. An adjective, or a second noun, may take the place of the participle in the Ablative Absolute construction:—²

• exiguā parte aestātis reliquā (B. G. 4.20), when but a small part of the summer was left (a small part of the summer remaining).
• L. Domitiō Ap. Claudiō cōnsulibus (id. 5.1), in the consulship of Lucius Domitius and Appius Claudius (Lucius Domitius and Appius Claudius [being] consuls). [The regular way of expressing a date, see § 424. g.]
• nīl dēspērandum Teucrō duce et auspice Teucrō (Hor. Od. 1.7.27), there should be no despair under Teucer's leadership and auspices (Teucer being leader, etc.).

b. A phrase or clause, used substantively, sometimes occurs as ablative absolute with a participle or an adjective:—

• incertō quid peterent (Liv. 28.36), as it was uncertain what they should aim at (it being uncertain, etc.).
• compertō vānum esse formīdinem (Tac. Ann. 1.66), when it was found that the alarm was groundless.
• cūr praetereātur dēmōnstrātō (Inv. 2.34), when the reason for omitting it has been explained (why it is passed by being explained).

c. A participle or an adjective is sometimes used adverbially in the ablative absolute without a substantive:—

• cōnsultō (Off. 1.27), on purpose (the matter having been deliberated on).
• mihi optātō vēneris (Att. 13.28.3), you will come in accordance with my wish.
• serēnō (Liv. 31.12), under a clear sky (it [being] clear).
• nec auspicātō nec lītātō (id. 5.38), with no auspices or favorable sacrifice.
• tranquillō, ut âiunt, quīlibet gubernātor est (Sen. Ep. 85.34), in good weather, as they say, any man's a pilot.