Letter from J. [James] Walker, Limehouse, London to Timothy Hackworth

He requests, for himself and Rastrick, results of substituting coke for coal 'for one day in the Locomotive Engine'. He gives details of relative weight of Hackworth's engine and Stephenson's six-wheeled Engine. He adds that he and Rastrick 'have only about two weeks for the consideration of our Report', and refers to Rastrick's request 'for the cost of the Repairs of an Engine for one year'.