At the present time a good deal of experimental work is being undertaken with page 18 oil-electric traction. Following the successful introduction of Diesel-electric railcars and trains in several countries, it has been suggested that oil-electric haulage with self-contained units, which are virtually power plants on wheels, offers a cheaper and more satisfactory system of transport than that afforded by electrification as it is commonly understood. Power houses, transmission lines, substations, and so on, are costly items, and one of the big arguments in favour of Diesel-electric traction is that equipment of this character is rendered unnecessary by the use of the oil-electric train. For the present, most of us will retain an open mind on the problem of the relative merits of electric and oil-electric haulage. In thisconnection, a most illuminating paper was recently submitted to the Institution of Civil Engineers, by Mr. H. W. Richards, Electrical Engineer of the L. and N.E. Railway.

Mr. Richards estimates that to deal with existing steam conditions in Britain the total oil-electric power required would be approximately 15,000,000 h.p. On an average load factor of 50 per cent. the total brake horse-power of the steam turbines, or other prime movers, needed in electric power stations to supply the hightension transmission system for electrified railways is put at 3,450,000 h.p. The weight required for electric tractors is estimated at 845,000 tons, and for oilelectric tractors 1,307,000 tons. In Mr. Richards’ view, the capital costs of electric and oil-electric traction approximate very closely at a traffic density of 4,000,000 for main-line services, and 2,000,000 for suburban services, but as the traffic density increases electric traction becomes progressively cheaper. Another interesting conclusion is that in the case of electric traction, at traffic densities greater than 2,500,000, a return of from 5 to 12 ½ per cent. would be earned, whereas, in the case of Diesel-electric traction the return would rarely reach 5 per cent. at traffic densities greater than 2,500,000. While refraining from any definite recommendation, the whole trend of Mr. Richards’ analysis was decidedly in favour of electric as against oil-electric traction.