PRESIDENTIAL ADDRESS. 



701 



cars, was for 247 passengers, giving an average of 1-4 ton of dead load to be 

 hauled by the engine per passenger assuming the train to be full. In the days 

 before corridor stock and dining-cars were invented the dead load to be hauled 

 was about a quarter of a ton per passenger for a full train. 



In a particular boat special, consisting of two first-class saloons, one second 

 and one third class vehicles, one first-class dining-car, one second and third class 

 dining-car, one kitchen-car, and two brake-vane, seating accommodation wae 

 provided, exclusive of the dining-cars, for 104 passengers, and the dead load to 

 be hauled averaged 2'72 tons per passenger. Notwithstanding this increase in the 

 dead load of luxurious accommodation, the fares are now less than in former days 

 on corresponding services. Similar developments have taken place in almost 

 every important service, and new express services are all characterised by heavy 

 trains and high speeds. 



Characteristic Energy-curves of Steam Locomotives. 



This steadily increasing demand for power necessarily directs attention to 

 the problem, What is the maximum power which can be obtained from a loco- 

 motive within the limits of the construction-gauge obtaining on British railways? 

 The answer to this can be found without much ambiguity from a diagram which 

 I have devised consisting of a set of typical characteristic energy-curves to repre- 

 sent the transference and transformation of energy in a steam locomotive, an 

 example of which is given in fig. 6. While examining the records of a large 



^Tvpigal Characteristic Enercv Curves- 



■ or Steam Locomoti v ES. 



1600000 



100000 200000 300000 4O0OOK 500000 600000 7OOO0O 



8T.U TRANSFERRED ACROSS H.S. PER MIN. 



Fig. 6. 



number of locomotive trials, I discovered that if the indicated horse-power Be 

 plotted against the rate at which heat energy is transferred across the boiler- 

 heating surface the points fall within a straight-line region, providing that the 

 regulator is always full open and that the power is regulated by means of the 

 reversing-lever— that is to say, by varying the cut-off in the cylinders. It is 

 assumed at the same time, of course, that the boiler-pressure is maintained 

 1910. z z 



