74 Explorations and Surveys for the Pacific Railroad. 



West, between its mouth and the 35th parallel, contains 1,600 

 square miles of fertile soil, which can be irrigated from the river. 



The plains south of the Gila in its lower course, and that 

 west of the Colorado, extending to the Coast range, called the 

 Colorado desert, as well as the contiguous portion of the Great 

 Basin are bare and exceedingly sterile in their aspect, and closely 

 resemble each other. The soil of the Colorado desert, and much 

 of this as well as other parts of the Great Basin, is however, fa- 

 vorably constituted for fertility, but the absence of the essential, 

 quickening element, water, leaves them utterly unproductive. 



West of the Coast, Sierra Nevada, and Cascade mountains the 

 country is better watered than that just considered ; and the soil 

 being mostly well constituted for fertility, is productive in pro- 

 portion to the yearly amount of precipitation and the means of 

 irrigation. * * * * 



NOTES ON THE SEVERAL ROUTES. 



Route near the forty-seventh and forty-ninth 'parallels of north 

 latitude. — The general direction of the Missouri from the Bocky 

 mountains to the Great Bend, in latitude 48° 30', is from west to 

 east, and thence to latitude 43° 30' southeast. The point where 

 the direction changes is reached from St. Paul, on the Missis- 

 sippi, by a line passing up on the east side of that river to Little 

 Falls, 109 miles, and there crossing it ; thence gaining the divide 

 between the waters of Hudson's Bay and those of the Missouri, 

 keeping on this divide, and approaching, in longitude 103°, 

 within a few miles of the 49th parallel ; then passing southerly, 

 between the 104th and 105th meridians, and entering the valley 

 of the Missouri river. The route then follows this valley to the 

 mouth of Milk river. The ground near the Missouri here be- 

 coming rough and broken, the route is obliged to leave it and 

 follow the valley of Milk river 187 miles ; then entering the 

 prairies, which near the mountains are more favorable for loca- 

 tion than near the Missouri river, it continues in a line nearly 

 parallel to the river, across its tributaries, the Marias, Teton, and 

 Sun rivers, and enters either Clark's or Cadotte's Pass, [near 

 latitude 47°]. * * * * * 



The summit ridge of Clark's Pass has an elevation of 6,323 

 feet, and requires a tunnel 2-J miles long, at an elevation of 5,300 

 feet. Its connexion with the main line of survey along the val- 

 ley of the Blackfoot river was not made, though "believed" 

 practicable, with grades of fifty feet per mile. The interval un- 

 examined is 4J miles long. This pass has been adopted by 

 Governor Stevens in the railroad estimate, and is probably prac- 

 ticable. 



The approach to the other pass (Cadotte's) is difficult, owing 

 to the numerous deep ravines of the tributaries of a branch of 



