Page:Across the Zodiac (Volume 2).djvu/188

 vast space was carried a bridge, supported by arches, and resting on pillars deeply imbedded in the submarine rock at a depth about equal to the height of the land on either side. The Martial seas are for the most part shallow, the landlocked gulfs being seldom 100 fathoms, and the deepest ocean soundings giving less than 1000. The vast and solid structure looked as light and airy as any suspension bridge across an Alpine ravine. This gigantic viaduct, about 500 Martial years old, is still the most magnificent achievement of engineering in this department. The main roads, connecting important cities or forming the principal routes of commerce in the absence of convenient river or sea carriage, are carried over gulfs, streams, ravines, and valleys, and through hills, as Terrestrial engineers have recently promised to carry railways over the minor inequalities of ground. That which we were following is an especially magnificent road, and signalised by several grand exhibitions of engineering daring and genius. It runs from Amacasfe for a thousand miles in one straight line direct as that of a Roman road, and with but half-a-dozen changes of level in the whole distance. It crossed in the space of a few miles a valley, or rather dell, 200 feet in depth, and with semi-perpendicular sides, and a stream wider than the Mississippi above the junction of the Ohio. Next it traversed the precipitous side of a hill for a distance of three or four miles, where Nature had not afforded foothold for a rabbit or a squirrel. The stupendous bridges and the magnificent open road cut in the side of the rock, its roof supported on the inside by the hill itself, on the outside by pillars left at regular intervals when the stone was cut, formed from one point