I determined, finally, to select the Atmospheric system of Railway Propulsion, and the great Iron Railway Bridges erected by him.
The length at which I have treated the former of these subjects demands some explanation, inasmuch as Robert Stephenson, far from promoting the Atmospheric system, was always one of its strongest opponents. But judges on whom I can fully rely were of opinion that it deserved a prominent place in his life, as well from the great interest he took in it, as from the extent to which it must have affected the whole course of Railway engineering. The facts of its history, with the results and lessons to be drawn from it, seemed likely soon to be forgotten, and were considered worthy of being put fully on record.
The preliminary chapter on Iron Bridges has been written in order to bring out more clearly the peculiarities and merits of the magnificent structures of this kind, to which probably Robert Stephenson will eventually owe his widest fame.
I have to acknowledge information kindly supplied by many friends in the profession.
The chapters which I have contributed to the work are XIV. in Vol. I., and II., III., IV., VIII., in Vol. II.