The second edition contained an famous "Preface" that included among other things an essay entitled "Emotion Recollected in Tranquility."  
The first edition was prefixed with an "Advertisement," warning that much of the content was "to be considered an experiment."  The second edition contained an famous "Preface" that included among other things an essay entitled "Emotion Recollected in Tranquility."  Some of the themes for pieces like "Idiot Boy," "Mad Mother," "Forsaken Indian," and "We Are Seven," were explained, though the other contributor offered his own theories fifteen years later in his Biographia Literaria.  It included such simple tales as "Simon Lee the Old Huntsman" and was always to have ended with "Lines composed above Tintern Abbey."  First published in 1798, FTP, name this collaborative poetry collection of Wordsworth and Coleridge.
The first edition was prefixed with an "Advertisement," warning that much of the content was "to be considered an experiment."  
Lyrical Ballads