The classic work The Railways of India with an Account of their Rise, Progress and Construction was written by Edward Davidson in 1868 with the aid of the records held in the India Office. This classic is now available online on the following page:
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http://books.google.co.in/books?id=zloOAAAAQAAJ&printsec=frontcover&dq=railways+of+india&source=bl&ots=RBNCxPL29W&sig=457f1MTXFm7clZD3dCyAIMmCcXo&hl=en#v=onepage&q&f=false