

220 HYPSOMETRIC ADDENDA. 



Mexico. The error amounts, for the western margin of the lake, to 

 almost 50 minutes of arc ; a difference of absolute longitude which 

 will appear less surprising, if it is remembered that my itinerary 

 map of Guanaxuato could only be based for 15 degrees of latitude 

 on compass surveys, or compass directions, for which I was indebted 

 to Don Pedro de Rivera. (Humboldt, Essai polit. sur la Nouvelle 

 Espagne, t. i. pp. 127136.) These directions being differently 

 combined by my early deceased fellow-laborer, Herr Friesen, and 

 myself, gave him as the result of his combinations 107 58' from 

 Paris, as the longitude of Santa Fe, and to me as the result of mine 

 107 13'. According to actual astronomical determinations since 

 obtained, the true longitude appears to be 108 22' W. of Paris, or 

 106 00' W. of Greenwich. The relative position of the beds of 

 fossil salt found in "thick strata of red clay," on the south-east of 

 the island-studded Great Salt Lake (my Laguna de Timpanogos), 

 and not far from the present Fort Mormon and the Utah Lake was 

 given with perfect correctness in my large map of Mexico. I may 

 refer on this point to the latest evidence of the traveller who made 

 the first well-assured determinations of geographical position in that 

 district : " The mineral or rock salt, of which a specimen is placed 

 in Congress Library, was found in the place marked by Humboldt 

 in his map of New Spain (northern half), as derived from the jour- 

 nal of the missionary Father Escalante, who attempted (1777) to 

 penetrate the unknown country from Santa Fe of New Mexico to 

 Monterey of the Pacific Ocean. South-east of the Lake Timpanogos 

 is the chain of the Wha-satch Mountains ; and in this, at the place 

 where Humboldt has written Montagnes de sel gemme, this mineral 

 is found." (Fremont, Geogr. Mem. of Upper California, 1848, pp. 

 8 and 67 ; compare Humboldt, Essai politique, t. ii. p. 261.) 



A great historical interest attaches to this part of the highland, 

 and more particularly to the country round the Lake of Timpanogos, 

 which is perhaps the same with the Lake of Teguayo, the ancestral 

 seat of the Aztecs. In their migration from Aztlan to Tula, and to 

 the Valley of Tenochtitlan (Mexico), this people made three halting- 

 places or stations, at which the ruins of the Casas grandes are still 

 to be seen. The first sojourn of the Aztecs was at the Lake of 



