Navigation through this channel is difficult and dangerous. Ndong Koni had charge of the wheel, and no white man could have surpassed him. A momentary glance at the surface of the water was sufficient to tell him what was beneath. He knew exactly the allowance to make for the strength of a whirlpool, or the force of the current in a short curve. An error of judgment, or a moment’s hesitation, in some places might have been our destruction. The first time I ascended this dangerous part of the river I engaged a pilot from one of the oldest towns; a man who had known the river all his life, who had seen it frequently at the lowest, and was therefore familiar with the channel; for the native does not forget a channel, but has a peculiarly tenacious memory for each snag and boulder that has occasionally been exposed to view. This pilot was picturesque, being dressed in a nondescript felt hat and scarcely anything else. We haggled for some time over the price of his services, but at last he agreed to come for a bar of soap and a dose of salts. As we ascended the river Ndong Koni stood at the wheel, in the bow, while the pilot stood immediately behind him, indicating with outstretched arms the channel and the dangers on either side. I stood bending over the engine, with one hand on the lever and the other on the throttle, in an attitude of strained attention. Several times we touched hidden snags that sent a shiver through the launch and strangely affected my own vertebræ; and once or twice we struck with such force as to disconnect the propeller. Suddenly the pilot began to “take on” like a maniac, yelling and calling to his ancestors, throwing his precious hat and pursuing it from one end of the cabin to the other, as if his mind had given way under the weight of responsibility. I left the engine long enough to rush forward, seize him by the neck and throw him into a corner. Then the truth dawned upon me: he had seen a fly and was trying to kill it. I have already said that this disposition towards the fly is an obsession with the native. In no other matter is he such a fool. But if he were engaged in a life-and-death combat with an enemy a sudden opportunity to kill a fly might prove his undoing. Upon our return we were sweeping down the river with the speed of a locomotive when I chanced to look out and found that we were passing Atakama, where we were intending to call. I shouted to the mate to stand by, and added some ungentle words of remonstrance at his stupidity in not observing that we had reached Atakama, where I had told him we were going to stop. I probably overdid the matter of remonstrance, for the mate got excited. He sprang to the anchor, and without a moment’s hesitation threw it overboard, while we were still going at nearly full speed with the swift current. The ensuing jar was such that it took me some time to realize that we were still afloat, and I could never afterwards pass the place without emotion.