We are indebted to Alain Alcouffe for pointing us to Thomas Humphrey's
comprehensive survey of cross-diagrams before Marshall.

I only wish that they and others gave more emphasis to the application of
marginal-cost pricing to DECREASING-cost operations (like mass transit, and
distribution networks for utilities of all kinds). Here is where the
deadweight loss is greatest, often making the difference between life and
death for the operation. This is what Hotelling was all about, and what is
so sorely neglected today. I surmise it was behind, in part, Marshall's idea
of taxing increasing-cost industries to subsidize decreasing-cost
industries, although it is not clear (to me) if Marshall had in mind
something specific like mass transit or some inchoate theoretical
possibility - I hope someone with specific insights into Marshall will chime
in and clear that up.

One thing very clear is that Howard Ellis and William Fellner, writing on
the subject in highly abstract terms, garbled it beyond possible
understanding - with the imprimatur of the AEA. 

Mason Gaffney