, "He _is gone_;
The birds _are flown_; The boy _is_ grown_; My friend _is arrived_."
The following mode of construction, is, in general, to be preferred;
"He _has_ gone; The birds _have_ flown; The boy _has_ grown; My
Friend _has_ arrived."

2. Active and neuter verbs may be conjugated by adding their present
participle to the auxiliary verb _to be_, through all its
variations; as, instead of, I teach, thou teachest, he teaches, &c.,
we may say, I am teaching, thou art teaching, he is teaching, &c.;
and, instead of, I taught, &c.; I was teaching, &c. This mode of
conjugation expresses the continuation of an action or state of
being; and has, on some occasions, a peculiar propriety, and
contributes to the harmony and precision of language. When the
present participle of an active verb is joined with the neuter verb
to be, the two words united, are, by some grammarians, denominated
an active verb, either transitive or intransitive, as the case may
be; as, "I am writing a letter; He is walking:" and when the present
participle of a neuter verb is thus employed, they term the
combination a neuter verb; as, "I am sitting; He is standing."
Others, in constructions like these, parse each word separately.
Either mode may be adopted.

* * * * *

III. DEFECTIVE VERBS.

DEFECTIVE VERBS are those which are used only in some of the moods and
tenses.

The principal of them are these.

_Pres. Tense. Imperf. Tense. Perfect or Passive Participle
is wanting_.

May, might. ------------
Can, could. ------------
Will, would. ------------
Shall, should. ------------
Must, must. ------------
Ought, ought. ------------
----- quoth. ------------

NOTE. _Must_ and _ought_ are not varied. _Ought_ and _quoth_ are
never used as auxiliaries. _Ought_ is always followed by a verb in
the infinitive mood, which verb determines its tenses. _Ought_ is in
the _present_ tense when the infinitive following it is in the
present; as, "He _ought_ to do it;" and _ought_ is in the
_imperfect_ tense when followed by the perfect of th