During the next eight or ten years very little progress was made, the vessels mostly in demand being colliers, in the construction of which no one thought of applying iron. About the year 1850, the carriage of coal by railway began seriously to affect the sale of north country coal in the London market, and it became essential, in the interest of the coal-owners and others, to devise some means of conveying the staple produce of the North Country to London in an expeditious, regular, and, at the same time, economical manner. To accomplish this object, Mr C. M. Palmer caused an iron screw-steamer to be designed in such a manner as to secure the greatest possible capacity, with engines only sufficiently powerful to ensure her making her voyages with regularity. This vessel (the _John Bowes_), the first screw collier, was built to carry 650 tons, and to steam about nine miles an hour. On her first voyage, she was laden with 650 tons of coals in four hours; in forty-eight hours she arrived in London; in twenty-four hours she discharged her cargo; and in forty-eight hours more she was again in the Tyne; so that, in five days, she performed successfully an amount of work that would have taken two average-sized sailing colliers upwards of a month to accomplish. To the success of this experiment may be attributed, in great measure, the subsequent and rapid development of iron shipbuilding in the Tyne and East Coast district. The district has maintained by far the largest share—almost amounting to a monopoly—in the production of the heavy-carrying, slow-speed type of cargo steamers, of which the _John Bowes_ may be said to have been the prototype. Statistics for the Tyne, as already explained, are not available to any extent until within recent years,[33] but from a paper on “The Construction of Iron Ships and the Progress of Iron Shipbuilding on the Tyne, Wear, and Tees,” written by Mr C. M. Palmer, and forming part of the work, “The Industrial Resources of the Tyne, Wear, and Tees,” published in connection with the British Association’s visit to Newcastle in 1863, it appears that the tonnage of iron ships launched from the Tyne during 1862 amounted to 32,175 tons, and during 1863, to 51,236 tons. Comparing this with the output for 1883—twenty years later—it is found that the figures are more than quadrupled, for in that year the output of the Tyne reached as much as 216,600 tons. In the year following the launch of the _John Bowes_, namely, in 1853, the first iron vessel built on the Wear, was released from its blocks. The Tees followed the example with great energy and considerable success, and on both these rivers trade in iron shipbuilding has been correspondingly developed.