The coal-fields on the eastern flank of the Pennines, therefore, namely, the Northern and the Yorkshire, are seen to be by far the most important in England. The carrying trade in coal is naturally very extensive, and may be considered here. The principal ports for the shipping of coal for export, set down in order of the amount shipped, also fall very nearly into topographical groups, thus:--Newcastle, South Shields and Blyth in the Northern District; Newport in Monmouthshire; Sunderland in the Northern District, Hull, Grimsby and Goole on the Humber, which forms the eastern outlet of the Yorkshire coal-fields; Hartlepool, in the Northern District, and Liverpool. The tonnage annually shipped ranges from about 4½ millions of tons in the case of Newcastle to some half a million in the case of Liverpool; but the export trade of Cardiff in South Wales far surpasses that of any English port, being more than three times that of Newcastle in 1903. The coastwise carrying trade is also important, the bulk being shared about equally by Sunderland, Newcastle, South Shields and Cardiff, while Liverpool has also a large share. Of the whole amount of coal received coastwise at English and Welsh ports (about 13½ million tons), London received considerably over one-half (nearly 8 million tons in 1903). The railways having the heaviest coal traffic are the North-Eastern, which monopolizes the traffic of Northumberland and Durham; the Midland, commanding the Derbyshire, Yorkshire and East Midland traffic, and some of the Welsh; the London & North Western, whose principal sources are the Lancashire, Staffordshire and South Welsh districts; the Great Western and the Taff Vale (South Welsh), with the Great Central, Lancashire & Yorkshire and Great Northern systems. In the face of railway competition, several of the canals maintain a fair traffic in coal, for which they are eminently suitable--the system of the Birmingham navigation, the Aire and Calder navigation of Yorkshire, and the Leeds and Liverpool navigation have the largest shares in this trade. Iron.