The one great difficulty in the way of development lay in the trouble experienced in getting the coal from the pit-banks to the river for loading into the keels, or barges, by which it would be conveyed to the sea-going colliers lying below the bridge at Newcastle. The established custom was to send the coal to the river by carts, or wains, or even in panniers slung across the backs of horses; and in Robert Edington's "Treatise on the Coal Trade" (1813) mention is made of various collieries which had up to 600 or 700 carts engaged in this service. Inasmuch, however, as the art of road-making in general was then still in its elementary stage, one can well imagine that, with all this traffic along them, the roads between the collieries and the Tyne must have been in a condition that added greatly both to the difficulties and to the cost of transport. Nicholas Wood, in his "Practical Treatise on Rail-roads" (1825), gives an extract, dated 1602, from the book of a Newcastle coal company, showing that "from tyme out of mynd" the coal carts had brought eight bolls--equal to about 17 cwt.--of coal to the river; but added that "of late several hath brought only, or scarce, seven," a fact sufficiently suggestive of the deplorable state to which the colliery roads had been reduced even at the opening of a century that was to bring about so great an increase in the demand for coal. Bad as the position was for the collieries located near to the Tyne, it was worse for those situate at any distance from the river, since, under the road conditions then prevailing, it was practically impossible for the owners of the latter collieries to get their coal to the river at all, or to secure {198}any share in a trade offering such great opportunities and undergoing such rapid expansion. The coal had but a nominal value so long as it could not be got away from the pit-banks. The first attempt to overcome the difficulties of the situation was in the direction of laying parallel courses of stone or wood for the waggon wheels to run upon; but here we have the equivalent of a partially-paved roadway rather than of actual rails. The latter came when the parallel wheel-courses of wood were reduced to what William Hutchinson, in his "View of Northumberland" (1778), calls "strings of wood," for the accommodation of "large unwieldy carriages or waggons."