a) With Adjectives; as,—
aqua ūtilis est bibendō, water is useful for drinking.
b) With Verbs (rarely); as,—
adfuī scrībendō, I was present at the writing.
3. Accusative. The Accusative of the Gerund is used only with Prepositions, chiefly ad and in to denote purpose; as,—
homō ad agendum nātus est, man is born for action.
4. Ablative. The Ablative of the Gerund is used—
a) Without a Preposition, as an Ablative of Means, Cause, etc. (see [§§ 218], [ 219]); as,—
mēns discendō alitur et cōgitandō, the mind is nourished by learning and reflection.
Themistoclēs maritimōs praedōnēs cōnsectandō mare tūtum reddidit, Themistocles made the sea safe by following up the pirates.
b) After the prepositions ā, dē, ex, in; as,—