"Now on, boys, on!" sung out the doctor, who saw what had occurred; and bringing our sticks down on our horses' backs, we dashed past the infuriated negroes, on whose heads Silva bestowed many a terrific whack with his stout stick, as they attempted to catch his rein.  We were followed closely by the guide and our valiant ally, old Surley, at whom several blows were aimed, but he escaped them all, and at full gallop we pushed over the sandy plain, pursued by our black assailants.  Happily they had no fire-arms, or we should have fared ill.  When we had got beyond their reach we pulled up and congratulated ourselves on our escape, while old Surley came in for his due share of praise and thanks. He wagged his tail and opened his mouth, as if he were about to speak and say, "I only did my duty, masters; you feed me well, and treat me kindly, and I love you, and am ready to fight for you, and do you any other service in my power, as I hope to prove whenever I have the opportunity."