Classic Poem

"There is Lowell, who's striving Parnassus to climb
With a whole bale of isms tied together with rhyme,
He might get on alone, spite of brambles and boulders,
But he can't with that bundle he has on his shoulders,
The top of the hill he will ne'er come nigh reaching
Till he learns the distinction 'twixt singing and preaching;
His lyre has some chords that would ring pretty well,
But he 'd rather by half make a drum of the shell,
And rattle away till he 's old as Methusalem,
At the head of a march to the last new Jerusalem.