+287.+ We have certain little phrases which we have used so often that
they have come to be used and regarded as single adverbs. They are such
phrases as _of course_, _of late_, _for good_, _of old_, _at all_, _at
length_, _by and by_, _over and over_, _again and again_, _through and
through_, _hand in hand_, _ere long_, _in vain_, _to and fro_, _up and
down_, _as usual_, _by far_, _at last_, _at least_, _in general_, _in
short_, etc. These words which we find used so often in these phrases we
may count as single adverbs.