London and North Western Railway in 1872, having driving-wheels 7 ft. 6 in. in diameter, weighed, without tenders, 27 tons 1 cwt.; but the compound engines now being made by Mr. Webb at the Crewe Works, having triple cylinders, and driving-wheels 6 ft. in diameter, weigh 42½ tons; while an even more powerful type of engine on the compound system, having 7-ft. driving wheels, weighs no less than 45½ tons, or, with the tender attached, 70½ tons.
The effect of this increase in the weight and dimensions of the vehicles employed is seen by the diagram given at page 159 (fig. 27), showing the growth which has taken place in the length and weight of some of the typical trains on the London and North Western Railway during the past five-and-twenty years. All the principal trains have been affected in the same way, and of course when trains, under ordinary circumstances, are of such great weight and length, they cannot easily be strengthened to meet any abnormal increase of traffic or sudden pressure, and it becomes necessary, instead, to run extra, or duplicate trains, thus adding in another way to the working expenses. The increased speed has also indirectly had the effect of adding very considerably to the number of trains run, and to the amount of train mileage. In order, for instance, to enable a train to run last year from London to Edinburgh in eight hours, it became not only necessary to maintain a high rate of speed throughout, but very few stoppages at intermediate places could be permitted, and other trains had to be run to serve the stations where the stoppages were omitted, and to enable the passengers from those stations to get on to other stations at which the train did stop.
Another cause which has tended greatly to increase
