Fell locomotive 

Hi, do you have any more information on the Fell's superchargers?  Clough says "turbochargers" (which I think is reasonable to infer as "mechanically-driven centrifugal"), but the small-scale GA drawing shows the sort of asymmetry that would suggest Roots (and not vane either). I have no idea who Holmes-Comerville were.  Do you have any better sources on the Fell?  I presume there are I. Loco E. papers on it, but I don't have anything myself.