Coal from different pits varies enormously in quality, and not only must the question of its heat-giving properties be studied, but there must also be considered its action on the firebox—i.e., whether, when burnt, it forms a running scar or a loose, white ash of a non-adherent nature. Before purchasing, the Home railways make chemical analyses and perform tests, under actual service conditions, of all likely coal supplies. After purchase, the coal supplied to the various depots is examined to ensure that it is up to sample, properly screened and hand-picked free from all foreign material. Coals used by the Home railways are of three grades. The first quality coal is supplied for express passenger work; second-grade coal goes to the engines working local passenger trains and important goods trains, while, for shunting engines, third-grade coal is employed. Every endeavour is made to reduce coal consumption on the Home railways, and to-day the average express passenger train of 450 tons runs something like 40 miles on one ton of coal. When it is realised that a big railway like the London and North Eastern spends no less than four million pounds sterling annually on locomotive coal, it will be appreciated that efforts to cut expenditure under this head to a minimum are fully justified.