were attached, furnishing the only instance of this higher kind of navigation among the American Indians.43 The other great road of the Incas lay through the level country between the Andes and the ocean. It was constructed in a different manner, as demanded by the nature of the ground, which was for the most part low, and much of it sandy. The causeway was raised on a high embankment of earth, and defended on either side by a parapet or wall of clay; and trees and odoriferous shrubs were planted along the margin, regaling the sense of the traveller with their perfumes, and refreshing him by their shades, so grateful under the burning sky of the tropics. In the strips of sandy waste, which occasionally intervened, where the light and volatile soil was incapable of sustaining a road, huge piles, many of them to be seen at this day, were driven into the ground to indicate the route to the traveller.44 All along these highways, caravansaries, or tambos, as they were called, were erected, at the distance of ten or twelve miles from each other, for the accommodation, more particularly, of the Inca and his suite, and those who journeyed on the public business. There were few other travellers in Peru. Some of these buildings were on an extensive scale, consisting of a fortress, barracks, and other military works, surrounded by a parapet of stone, and covering a large tract of ground. These were evidently destined for the accommodation of the imperial armies, when on their march across the country. The care of the great roads was committed to the districts through which they passed, and a large number of hands was constantly employed under the Incas to keep them in repair. This was the more easily done in a country where the mode of travelling was altogether on foot; though the roads are said to have been so nicely constructed, that a carriage might have rolled over them as securely as on any of the great roads of Europe.45 Still, in a region where the elements of fire and water are both actively at work in the business of destruction, they must, without constant supervision, have gradually gone to decay. Such has been their fate under the Spanish conquerors, who took no care to enforce the admirable system for their preservation adopted by the Incas. Yet the broken portions that still survive, here and there, like the fragments of the great Roman roads scattered over Europe, bear evidence to their primitive grandeur, and have drawn forth the eulogium from a discriminating traveller, usually not too profuse in his panegyric, that "the roads of the Incas were among the most useful and stupendous works ever executed by man." 46