“Well, it seems to be the only thing to do--to try a trip down it,” said Mr. Hotchkiss, when they had held a consultation about it. “River travel is certainly easier than on land, in a jungle, and we’ll have to cross it sooner or later, for I have a general idea now where the country lies that we are trying to reach.” “But how are we going to go down the river when we have no boats?” asked C. C. Piper. “We can’t swim--and I’ve had enough of that anyhow, since leaving the California coast.” “We can get the natives to build a big raft,” suggested Mr. Hotchkiss. “On that we can float down, but we can’t very well take the animals,” for they still had with them their riding mules and those that carried packs. Several of the animals had died from the bite of the tse-tse fly, but as the expedition was constantly using up food and supplies, the burdens of the dead animals were transferred to the heads of the porters. “What can we do with the animals?” asked Mr. Duncan. “Leave them back at the village we passed a little while ago,” suggested the former soldier, and this was agreed to. Happy One declared that his men could soon build a raft that would carry them all, but when it came to the making of it the whites found it better to superintend the details themselves. “They’d have it come apart in the middle of the river the way they were binding the logs together with vines,” said the sergeant as he made the blacks correct some of their faults. “We want it substantially made.” But when the rafts were about done (for they decided to make two) they were ample for all. The animals were to be left behind, and, with the packs and bundles, the moving picture cameras and films, those already exposed and new ones, the start down the river was to be made some morning soon. While the raft-building was going on Joe and Blake had some opportunity to go out into the jungle, near the river camp, and make moving pictures. Though they got no remarkable ones they did succeed in filming a rhinoceros upon whose back were a number of tick birds. These curious feathered creatures are to the rhinoceros what the pilot fish are to the shark. They warn of danger. The big-horned animals of Africa, in common with most of the mammals, are infested with ticks, an insect that lives by sucking the blood of the beasts. Tick birds feed on these ticks and often perch on the backs of the rhinoceroses and pick them off. But the birds are very shy and easily made aware of danger, not only to themselves but to their animal feeding-ground. They fly off at the first alarm, and as soon as they go the rhinoceros knows that he must look out for himself. Once the tick birds fly from his back he begins to use the natural faculties most useful to him. Blake and Joe were getting some fine pictures of a rhino feeding, and as the wind was right, the beast did not scent them. Presently, however, the tick birds became aware of something unusual going on. CHAPTER XXI THE LONE MESSENGER