Impromptu on Writing a Letter Without Having Anything to Say

So have I seen the maids in vain
Tumble and teaze a tangled skein;
They bite the lip, they scratch the head,
And cry "the deuce is in the thread,"
They torture it, and jerk it round,
Till the right end at last is found,
Then wind and wind and wind away,
And what was work is changed to play.