6.  The Perfect Passive Participle in combination with a noun is sometimes equivalent to an abstract noun with a dependent Genitive; as,—­

    post urbem conditam, after the founding of the city;

    Quinctius defensus, the defense of Quinctius;

    quibus animus occupatus, the preoccupation of the mind with which.

7.  Habeo sometimes takes a Perfect Passive Participle in the Predicate construction with a force not far removed from that of the Perfect or Pluperfect Indicative; as,—­

    equitatus quem coactum habebat, the cavalry which he had collected.

8.  The Gerundive denotes obligation, necessity, etc.  Like other Participles it may be used either as Attributive or Predicate.

  a) Less frequently as Attributive.  Thus:—­

    liber legendus, a book worth reading;

    leges observandae, laws deserving of observance.

  b) More frequently as Predicate.

    1) In the Passive Periphrastic Conjugation (amandus est, etc.).  In this
    use Intransitive Verbs can be used only impersonally, but admit their
    ordinary case-construction (Gen., Dat., Abl.); as,—­

    veniendum est, it is necessary to come;

    obliviscendum est offensarum, one must forget injuries;

    numquam proditori credendum est, you must never trust a traitor;

    suo cuique utendum est judicio, every man must use his own judgment.

    2) After curo, provide for; do, trado, give over; relinquo,
    leave; concedo, hand over, and some other verbs, instead of an
    object clause, or to denote purpose; as,—­

    Caesar pontem in Arari faciendum curavit, Caesar provided for the
    construction of a bridge over the Arar;

    imperator urbem militibus diripiendam concessit, the general handed
    over the city to the soldiers to plunder.

9.  For the Gerundive as the equivalent of the Gerund, see Sec. 339, 1.

THE GERUND.

338.  As a verbal noun the Gerund admits noun constructions as follows:—­

1.  Genitive.  The Genitive of the Gerund is used—­

  a) With Nouns, as objective or Appositional Genitive (see Sec. 200, 202);
  as,—­

    cupiditas dominandi, desire of ruling;

    ars scribendi, the art of writing.

  b) With Adjectives; as,—­

    cupidus audiendi, desirous of hearing.

  c) With causa, gratia; as,—­

    discendi causa, for the sake of learning.

2.  Dative.  The Dative of the Gerund is used—­

  a) With Adjectives; as,—­

    aqua utilis est bibendo, water is useful for drinking.

  b) With Verbs (rarely); as,—­