376 Observations on the Physical Geography 



Art. XXXIV. — Observations on some points in the Physical Ge- 

 ography of Oregon and Upper California ; by James D. Dana. # 



The heights of the Rocky mountains which form the natural 

 division between the territory of Middle and Western America, 

 range along a nearly north-northeast course at a distance of six 

 to eight hundred miles from the Pacific coast. These mountains 

 properly include the whole breadth of country west of the Mis- 

 sissippi plains. The swelling of the land begins from western 

 Missouri and very slowly rises with a slope not exceeding seven 

 or eight feet to the mile, until it reaches an elevation of five to 

 eight thousand feet. About the summit the surface becomes 

 broken with ridges that rise still higher by three to six thousand 

 feet, and the Wind River mountains, according to Fremont, stand 

 with their bleak tops 13,570 above the sea. The traveller makes 

 his journey by the South Pass,f without an ascent beyond 7,490 

 feet, and the difficulties are so slight that loaded wagons may be 

 transported across. Thence after a while a descent is com- 

 menced, and although hills and mountain ridges are encountered, 

 the surface, viewed in its wide extent, continues to decline to the 

 ocean. The accompanying sections, one from Fremont,! the 

 other from Emory,$ are excellent illustrations of this great fea- 

 ture in the physical geography of the west. The ridges at top 



Profile of the route from the mouth of the Kansas to the Pacific, bv J. C. Fremont, 

 in 1843. Vertical scale to horizontal as 30 to 1. The intervals between the hori- 

 zontal lines are each 2,000 feet; a. Mouth of Kansas River, b. St. Vrain's Fort. 

 c. Laramie River, d. South Pass. e. Dividing range. /. Beer Springs, ff. Great 

 Salt Lake. h. Fort Hall. i. Crossing of Snake River, k. Blue Mountains. I Fort 

 Wftllawalla. m. Dalles, n. Cascades, o. Fort Vancouver, p. Mount St, Helen s. 



* In part from the Author's Geological Report of Exp. Exped. under Capt. < 

 Wilko,, IJ. S. N. ^ F " 



fThe South Pass is at the headwut.rs of the North Fork of the Nebr ka or 

 Platte River. Lewis and Clarke's Pass is at the headwaters of the Jefferson river, 

 a branch of the Yellow Stone ; it is covered with snow. 



\ Rep. Expl. Exped., to the Rockv Mountains, in 1842, to Oregon and California, 

 in 1843, 1844; by Brevet Captain" J. C. Fremont. Washington, 1846. See this 

 Jour., iii, 192. 1847. 



§ Notes on a Military Reconnoisance from Fort Leavenworth in Missouri, to ^a» 

 Diego in California, in 1846 ; by Brevet Major W. EL Emory. See this Jour., n, 

 367,1848. 



