But there seemed to be some difficulty about persuading the mules to cross it. As the leaders felt the water growing deeper and the sandy bank giving way beneath them, they sprang back in terror, and threw the whole team into confusion. The wagon came to a standstill, and everybody in the vicinity realized its danger. The driver, feeling that the need for silence and caution was past, began to shout at his mules, and the reports of his blacksnake whip rang out like pistol-shots.