Many new vehicles have in recent times been introduced on the Home group lines for handling postal mails. This is a most important business, demanding the closest co-operation between the railways and the postal authorities. The special mail cars employed in Britain consist of mobile sorting units and stowage cars. In some instances, complete trains of postal vehicles are run. In others, one or more mail cars are attached to the ordinary passenger trains. The normal length of the sorting carriages is 60 ft. Along one side of the car are arranged the sorting tables and racks. On the opposite side there is fixed the apparatus for receiving and delivering mail-bags while travelling at high speed. The heaviest travelling post offices are what are known as the Up and Down Specials on the L. M. & S. The Up Special leaves Aberdeen at 3.25 p.m. daily, and arrives at Euston Station, London, at 3.55 a.m. The Down Special leaves Euston at 8.30 p.m., and arrives Aberdeen 7.52 a.m. These two trains handle, annually, 105,000,000 pieces of mail. In the case of the Down Special, 700 bags of mail are received daily from 230 offices for opening and sorting on page 39 the train. Some 650 bags of mail are despatched daily to 350 offices, in addition to through mails. On each trip, 68 letter pouches are transferred from the train to line-side collecting nets, and 52 pouches are picked up.