HYPSOMETRIC ADDENDA. 219 



1777 English, feet higher than the Chimborazo. (Fitz Hoy, Voyages 

 of the Adventure and Beagle, 1839, vol. ii. p. 481; Darwin, Journal 

 of Researches, 1845, pp. 223 and 291.) According to more recent 

 calculations, the height of Acongagua is given as 22,431 French, or 

 23,907 English feet. (Mary Somerville, Physical Geogr. 1849, 

 vol. ii. p. 425.) 



Our knowledge of the systems of mountains which, north of the 

 parallels of 30 and 31 N. lat., are called the Rocky Mountains 

 and the Sierra Nevada of California, has received most important 

 additions, geologically, botanically, hypsometrically, and geographi- 

 cally by astronomical determinations of position, from the excellent 

 works of Charles Fremont (Geographical Memoir upon Upper Cali- 

 fornia, an illustration of his Map of Oregon and California, 1848) ; 

 of Dr. Wislizenus (Memoir of a Tour to Northern Mexico, connected 

 with Col. Doniphan's Expedition, 1848) ; and of Lieutenants Abert 

 and Peck (Expedition on the Upper Arkansas, 1845; and Exami- 

 nation of New Mexico in 1846 and 1847). There prevails through- 

 out these different North American works a true scientific spirit, 

 which is deserving of the greatest commendation. The remarkable 

 elevated plain, which rises to an uninterrupted height of four or five 

 thousand French (4260 and 5330 English) feet, between the Rocky 

 Mountains and the Sierra Nevada of California, of which I have 

 spoken in p. 54, and which is called the Great Basin, forms an in- 

 land closed river basin, and has hot springs and salt lakes. None 

 of its rivers Bear River, Carson River, and Humboldt River find 

 their way to the sea. The Lake, which I was led by combinations 

 and inferences to represent, in the great Map of Mexico drawn by 

 me in 1804, under the name of Lake Timpanogos, is the great Salt 

 Lake of Fremont's Map : it is sixty geographical miles long, from 

 north to south, and ten broad ; and it communicates with the fresh 

 water lake of Utah, which is situated at a higher level, and receives 

 the Timpanogos or Timpanaozu River, which enters it from the east- 

 ward, in lat. 40 13'. The circumstance of the Timpanogos Lake 

 of my map not having been placed by me sufficiently far to the north 

 and west, is to be attributed to the entire want, at that time, of any 

 astronomical determinations of the position of Santa Fe, in New 



