_Communications._--Owing to its proximity to the metropolis, Hertfordshire is particularly well served by railways. On the eastern border there is the Great Eastern (Cambridge line) with branches to Hertford and to Buntingford. The main line of the Great Northern passes through the centre by Hatfield, Stevenage and Hitchin, with branches from Hatfield to Hertford, to St Albans and to Luton and Dunstable, and from Hitchin to Baldock, Royston and so to Cambridge. The Midland passes through St Albans and Harpenden, with a branch to Hemel Hempstead. The London & North-Western traverses the south-west by Watford, Berkhampstead and Tring, with branches to Rickmansworth and to St Albans. The Metropolitan & Great Central joint line serves Rickmansworth, and suburban lines of the Great Northern the Barnet district. The existence of these communications has combined with the natural attractions of the county to cause many villages to become large residential centres. Water communications are supplied from Hertford, Ware and Bishop Stortford, southward to the Thames by the Lea and Stort Navigation; and the Grand Junction canal from London to the north-west traverses the south-western corner of the county by Rickmansworth and Berkhampstead. Three great highways from London to the north traverse the county. The Holyhead Road passes Chipping Barnet, South Mimms and St Albans, quitting the county near Dunstable. The Great North Road branches from the Holyhead Road at Barnet, and passes Potter's Bar, Hatfield, Stevenage and Baldock, with a branch from Welwyn to Hitchin and beyond. Another road follows the Lea valley to Ware, whence it runs to Royston, being here coincident with the Roman Ermine Street and known as the Old North Road.