Here is my answer to the axis reversal question, one that has been in my  
text book since its first edition in 1963  
  
"Readers trained in other disciplines often wonder why economists plot  
demand curves with price on the vertical axis. The normal conven?tion, which  
puts the independent variable (the variable that does the explaining) on the  
horizontal axis and the dependent variable (the variable that is explained)  
on the vertical axis, calls for price to be plotted on the horizontal axis  
and quantity on the vertical axis.  
  
The axis reversal-now enshrined by a century of usage-arose as follows. The  
analysis of the competitive market that we use today stems from the French  
economist Leon Walras (1834-1910), in whose theory quantity was the  
dependent variable. Graphical analysis in economics, however, was  
popularized by the English economist Alfred Marshall (1842-1924), in whose  
theory price was the dependent variable. Economists continue to use Walras's  
theory and Marshall's graphical representation, and thus draw the diagram  
with the independent and dependent variables reversed-to the everlasting  
confusion of readers trained in other disci?plines. In virtually every other  
graph in economics the axes are labelled conventionally, with the dependent  
variable on the vertical axis."  
  
  
Lipsey, Richard G. and Alec Chrystal (1995), An Introduction to Positive  
Economics (eighth edition), (Oxford: Oxford University Press), pp 64 (FN  
#3).  
  
Richard G. Lipsey