in the perfect condition which is essential. It is also in a great measure the high rate of speed at which the trains have to be run that necessitates the elaborate and complicated system of signalling and interlocking which has been described in Chapters V. and VI.
Again there has been a very striking increase in the size and weight of the carriages employed for the conveyance of passengers, arising from the popular demand for improved accommodation, and the extent to which that demand has been met.
The standard third class carriage of 1872, for example, was 30½ feet long, and weighed 10 tons, but the standard third class carriage of 1889 is 42 feet in length, and weighs upwards of 18 tons. The carriage of 1872 was capable of seating 50 passengers, but that of 1889 only seats 20 more, or 70 in all, so that while the weight of the vehicle has increased by 80 per cent, the seating capacity has only increased by 40 per cent.—in other words, the weight has increased in double the ratio of the accommodation provided. To take another illustration, the standard composite carriage built by the London and North Western Company in 1872, 30 feet 5 inches in length, weighed 10 tons 8 cwt, but those of the latest type, built recently, measure 42 feet in length and weigh from 18 to 19 tons. These contain lavatory accommodation for the first class compartments, and a cupboard for luggage, and they only provide seats for 44 passengers, as against 36 who could be conveyed in the smaller vehicle of the earlier period.
To keep pace with the increased weight of the vehicles, the power and weight of the engines employed to draw them has also had to be correspondingly augmented. The most powerful passenger engines in use on the
