This question has no pertinence in our times, since, by reason of being shod with iron, our horses do not injure their hoofs by running upon the rock. Horse-shoeing was, however, unknown to the Hebrews, and is of comparatively modern introduction. Bishop Lowth states that the shoes of leather and of iron mentioned by Greek and Roman writers, as well as the silver and the gold shoes with which Nero and Poppea shod their mules, enclosed the whole hoof as in a case, or as a shoe does a man’s foot, and were bound or tied on, and even these were exceptional cases. In ordinary instances no shoes of any kind were used. We can thus see how, with hoofs unprotected; the horses could not be expected to run upon a rock. No doubt Amos had this in mind. Isaiah also, in describing the character of the army that should come with destructive judgments upon Judah, says that “their horses’ hoofs shall be counted like flint” (Isa. 5: 28). A hard hoof must have been a very desirable quality in a horse, when the art of protecting the foot with iron shoes was unknown.