CHAPTER VII. OUTPUT OF TONNAGE IN THE PRINCIPAL DISTRICTS. With the change from wood to iron shipbuilding, and with the development of propulsion by steam instead of sails, the shipbuilding industry has become localised and concentrated in those districts which, besides possessing the _sine qua non_ of ready outlet to the vast ocean, are specially favoured in being the repositories of immense natural wealth in the form of coal and ores. What may now fairly be considered the great centres of shipbuilding are the valleys of the Clyde, Tyne, Wear, and Tees, and also the Thames and Mersey, although these latter rivers have for a considerable number of years been overshadowed as building centres by the immensity of their shipping. In several other districts, of course, shipbuilding is carried on to a considerable extent, and some of these may yet attain much greater importance than they at present possess. Barrow-in-Furness, notwithstanding the remarkable progress of recent years, is still advancing. Belfast occupies a prominent position, not alone because of the large annual output of tonnage, but by reason of the number of high-class ocean steamships which have been, and continue to be, built there. Dundee, Leith, Hull, Southampton, and other places throughout the United Kingdom, are not without claims to recognition on account of the shipbuilding carried on. The supremacy of one shipbuilding centre over another in the matter of work accomplished, both with regard to its character and its quantity, not infrequently forms the subject of comment in the columns of journals circulating in the districts concerned. The publication, by these journals, at the close of each year, of the returns of new tonnage produced by the various firms, affords an opportunity for vaunting on such matters, and it is, as a rule, taken advantage of by the compilers of the statements, who are usually members of the staff on the journals in question. These statements, through the interesting nature of the statistics they contain, are widely read, and the labour attaching to their preparation must indeed be considerable. The figures are, as a rule, supplied by the shipbuilders themselves, and from a summation of these the compiler draws his conclusions. The accuracy of the returns and the fairness of the comments based upon them, if not always completely satisfactory, are thus seen to be matters for which the compiler is not wholly responsible.