A zillion or so years ago (mid-1970s) H. Scott Gordon wrote a paper  
called, appropriately, "Why Did Marshall Transpose the Axis?" As you  
might guess the argument was basically because of the welfare-economics  
motivations and the relationship between quantity and marginal utility.  
Since quantity is the independent variable in a marginal utility  
function it should be on the horizontal axis, as it should for the  
demand curve relating quantity to demand price. The paper was certainly  
undergraduate accessible, but unfortunately I do not think it was ever  
published and it was pre-electronic. I think I still have a hard copy  
somewhere if you want me to send it to you.  
  
D. Wade Hands