103 



tus, agaves, and a few other kinds of plants whose bark serves the purpo- 

 ses of leaves, except in places where the roots can reach water. The pro- 

 longed drought dries up all the rivulets in the low land or "tierra calien- 

 ie" as it is called locally, but the immense rock masses of the plateau — 

 rightly named Sierra Madre, mother of mountains — store up and give out 

 a perennial stream, never falling below 64,000 cubic feet per minute. 



The Puerte is 275 miles long from source to mouth, and the united 

 river for a third of the whole length' flows through the low plain the re- 

 maining part and all the chief tributaries pass through rugged foot hills 

 and in deep canons worn in the Sierra itsel £. 



This country was traversed by the author in 1897 from west to east, 

 but it will be more convenient for the purpose of description to start near 

 the watershed. 



Proceeding therefore from the town of Chihuahua on the Mexican 

 tientra) Railway, one traverses the central plain, gradually rising from 

 east to west towards the wave crest of the great slope; for the first 70 mi- 

 les the road or track goes over a rugged country composed of weathered 

 dark volcanic rocks, arid studded with abrupt hills which rise like islands 

 in a stormy sea of lava. Thers is little surface soil, and, except a few sha- 

 llow valleys like that of Sta. Isabel, the region, owing to drought, is a de- 

 sert. After reaching Oosihuiriachic, a town depending on very ancient 

 and rich silver and lead mines, the llanos are seen stretching upward to- 

 ward the watershed of the continent; they are very smooth, broken by 

 few arroyos, and covered with grass forming a good cattle country where- 

 ver water is obtainable. Thirty miles to the N. W. of the town is a group 

 of rocky hills whence streams flow in three directions— south-east to the 

 Rio Conchos, which joins the Rio Grande del Norte, and discharges into 

 the Gulf of Mexico — north to the Rio de Sta Maria, an inland sytem of 

 drainage ending in a salt lagoon near the United States frontier — and west 

 through the mountains to the Gulf of California. 



The llanos preserve the original slope and surface of the old lava 

 flows, and are protected from denudation by their lofty elevation, the small 

 rainfall on the inland side of the mountains, and by a coating of soil with 

 permanent gras. (1) Travelling over them, is a pleasing contrast to pro- 

 gress over the stony plain, and the antique-looking; leather-slung coa- 

 ches drawn by teams of eight or ten, well-matched, closely-clipped, whi- 

 te mules go at a fast canter over the smooth surface. Towards the summit 

 of the slope rounded hills studded with dwarf oaks appear, and the ground 

 is broken; but some attempt at grading the tracks enables wheeled vehi- 



(1) There are also alluvial deposits in this region, 

 ternary age. 



containing bone remains Of Qua- 



