Page:Horse shoes and horse shoeing.djvu/638

 — a circumstance which raised the price of these animals considerably above that of horses. But even the employment of mules was limited, because of the damage done to their feet on roads which were generally so badly made, if made at all, that travelling on them was only possible for short distances. It was, doubtless, in a great measure to obviate these inconveniences that the Romans constructed their wonderful strata. On such paved roads, cavalry or horses drawing light vehicles would probably travel a number of days without shoes; and it may be that heavy loads in carriages were transported on them for some distance by long teams of mules, as observed by Martial, in the beginning of our era: 'Longæ mulorum mandras.'

Beyond these roads, however, quadrupeds were scarcely available for drawing heavy weights; and human strength, together with the ingenuity of the Roman engineers, was enlisted to convey, by means of rollers, levers, and various other appliances, the materials destined for building or other purposes. Even in Rome, and in many other cities built before shoeing had become general, the main thoroughfares were too narrow to permit carriages laden with bulky articles to pass. The object of this was probably to make them shady, and protect them from the sweeping winter winds, as well as to impede an enemy should he attempt to enter. All transport, therefore, must have been accomplished at an immense sacrifice of manual labour, which to us now would appear appalling. In the north of China, where horses are