The wooden tramway was the first improvement over the ordinary road. The idea once originated, various types were soon introduced, and the sketch shown in Fig. 227 illustrates one which appears to have been early suggested and largely adopted. Wooden cross-sleepers, A, A, were placed at convenient spaces, and on the top of these strong timber planks or beams, B, B, were spiked at proper distances to suit the wheels of the waggons or four-wheel trucks, which had flat tyres like ordinary carts. The spaces between the sleepers were filled in with gravel or broken stone to form a roadway or hauling path for the horses. A little later _double rails_ were introduced, by placing a second or upper timber on the top of the lower one, as in Fig. 228. [Illustration: Fig. 227, 228, 229, 230, 231, 232, 233, 234, 235] This double rail arrangement not only strengthened the framework, but by increasing the height allowed a greater quantity of suitable 184 material to be placed over the sleepers to protect them from wear by the horses’ feet. It can be easily understood that a wooden tramway could not be very durable. It would be affected by the sun, rain, and snow, and particles of sand and gravel thrown on to the tram beams from the hauling path would hasten the abrading or wearing away of the soft portions of the timber into hollows, leaving the hard knots standing out as projections. The uneven surface would produce a series of blows every time a loaded truck passed along, loosening the pieces and rendering the repairs constant and expensive. To obviate the rapid wear of the tram-timbers continuous narrow bars of wrought-iron were fastened on to the running-surfaces; these in a measure prolonged the life of the timbers, but at the same time added to the number of the pieces and fastenings to be maintained. Primitive as this description of road appears to be, it was in use for many years in some parts of the United States of America, and even after the introduction of the early locomotives; timber was abundant and cheap, and iron in any form was costly. These long thin strips of iron, placed as in Fig. 232, had a tendency to become unfastened at the ends, and to curl up in a very alarming manner, which earned for them the soubriquet of _snake heads_. Although iron was only used to a limited extent in the first instance, it was soon found to be a much more suitable material for a tram-path than the best timber. As a next progressive step we find that the tram-plates were made entirely of iron, of full width for the wheel-tyres, and with a guiding flange to keep the wheels on the proper track. In some cases the guiding flanges were placed inside the wheels, as in Figs. 229 and 230, and in others outside, as in Fig. 231. With the former plan a thicker covering of gravel or broken stones could be laid down to protect the sleepers under the horse-path.