His uncle, the one who had gotten Ken letters from the Forestry Department at Washington, had been proud of Ken's Arizona achievements, This uncle was a member of the American Geographical Society and a fellow of the New York Museum of Natural History. He wanted Ken to try his hand at field work in the jungle of Mexico, and if that was successful, then to explore the ruined cities of wild Yucatan. If Ken made good as an explorer his reward was to be a trip to Equatorial Africa after big game. And of course that trip meant opportunity to gee England and France, and, what meant more to Ken, a chance to see the great forests of Germany, where forestry had been carried on for three hundred years.

In spite of the fact that the inducement was irresistible, and that Ken's father was as proud and eager as Ken's uncle to have him make a name for himself, and that Hal would be allowed to go with him, Ken had hesitated. There was the responsibility for Hal and the absolute certainty that Hal could DA keep out of mischief. Still Ken simply could not have gone to Mexico leaving his brother at home broken-hearted.

At last the thing had been decided. It was Hal's ambition to be a naturalist and to collect specimens, and the uncle had held out possible recognition from the Smithsonian Institution at Washington. Perhaps he might find a new variety of some animal to which the scientists would attach his name. Then the lad was passionately eager to see Ken win that trip to Africa. There had been much study of maps and books of travel, science, and natural history. There had been the most careful instruction and equipment for semi-tropical camp life. The uncle had given Ken valuable lessons in map-drawing, in estimating distance and topography, and he had indicated any one of several rivers in the jungle belt of Mexico. Traversing one hundred miles of unknown jungle river, with intelligent observation and accurate reports, would win the prize for Ken Ward. Now the race was on. Would Ken win?

Presently the train crossed a bridge. Ken Ward had a brief glance at clear green water, at great cypress-trees, gray and graceful with long, silvery, waving moss, and at the tangled, colorful banks. A water-fowl black as coal, with white-crested wings, skimmed the water in swift wild flight, to disappear up the shady river-lane. Then the train clattered on, and, a mile or more beyond the bridge, stopped at a station called Valles. In the distance could be seen the thatched palm-leaf huts and red-tiled roofs of a hamlet.

The boys got out to stretch their legs. The warm, sweet, balmy air was a new and novel thing to them. They strolled up and down the gravel walk, watching the natives. Hal said he rather liked the looks of their brown bare feet and the thin cotton trousers and shirts, but he fancied the enormous sombreros were too heavy and unwieldy. Ken spoke to several pleasant-faced Mexicans, each of whom replied: "No sabe, Senor."

The ticket agent at the station was an American, and from the way he smiled and spoke Ken knew he was more than glad to see one of his own kind. So, after Ken had replied to many questions about the States, he began to ask some of his own.

"What's the name of the waterfall we passed?"

"Micas Falls," replied the agent.

"And the river?"

"It's called the Santa Rosa."

"Where does it go?"

The agent did not know, except that it disappeared in the jungle. Southward the country was wild. The villages were few and all along the railroad; and at Valles the river swung away to the southwest.

"But it must flow into the Panuco River," said Ken. He had studied maps of Mexico and had learned all that it was possible to learn before he undertook the journey.

"Why, yes, it must find the Panuco somewhere down over the mountain," answered the agent.

" Then there are rapids in this little river?" asked Ken, in growing interest.

"Well, I guess. It's all rapids."

"How far to Tampico by rail?" went on Ken.

"Something over a hundred miles."

"Any game in the jungle hereabouts--or along the Santa Rosa?" continued Ken.

The man laughed, and laughed in such a way that Ken did not need his assertion that it was not safe to go into the jungle.

Whereupon Ken Ward became so thoughtful that he did not hear the talk that followed between the agent and Hal. The engine bell roused him into action, and with Hal he hurried back to their seats. And then the train sped on.