Dr. Bronson and his young companions travelled thus down the eastern slope of the Andes into the valley of the Beni. Ten days after their departure from Huancané they reached the point where it was necessary to leave the mules; the drivers were paid off and discharged, and were ready to start back to the shore of Lake Titicaca. Fortunately, they found an engagement with a merchant who had some goods to transport over the mountains, and was glad to secure their services. For the next thirty miles the way was so steep and rough as to be impracticable for even the sure-footed mule. Travellers have the choice of the _silla_ or to go on foot, while their baggage is carried on the backs of men. Frank and Fred looked doubtingly at the silla, and so did the Doctor. They preferred to walk, but at the suggestion of Dr. Bronson each of the party engaged a silla, to be used whenever he was inclined to it. Perhaps you are wondering what the silla is. It is thus described by Fred: [Illustration: TRAVELLING BY SILLA.] "A bamboo chair is strapped to the back of the _sillero_, or porter, by means of belts going around his chest and another which crosses his forehead. The traveller sits in this chair, with his feet supported on a step which forms part of the conveyance. He must sit perfectly still while the sillero is in motion, as the least change of position might cause the porter to stumble and fall, and a fall among the rocks is liable to be a very serious affair for both parties. "Mr. Horton, in his 'Twenty Months in the Andes,' tells of a Spanish officer who was travelling in this way, and wore a pair of spurs with which he occasionally prodded the porter, to urge him to greater speed. The latter took a fearful revenge. "Maddened with the pain produced by the cruel spurs, he pitched his rider headlong over a precipice, where there was a sheer fall of two or three hundred feet. The officer was killed instantly, and before his companions could secure the sillero the latter fled into the forest and escaped. The scene of this occurrence is pointed out, and there is little doubt of the truth of the story. It is easy to see that the traveller is entirely at the mercy of his carrier; knowing this, we were careful to secure the good-will of our silleros by promising an extra payment if they went through without accident.