6 AN ACCOUNT OF THE 



The best ascent to it was on the eastern side, both the northern and the western 

 being too precipitous for loaded animals. Indeed, the ascent of the western slope is 

 almost impracticable for even pedestrians. To the east, the Andes form a serrated 

 but apparently unbroken chain, with lateral spurs at unequal distances extending 

 to the westward. The greatest depression bore E. by N. from our camp, the crests 

 there being estimated to form an angle of 8° with the horizon and 20 miles distant 

 in a straight line, corresponding to an elevation of about 15,000 feet. From a 

 mean of the barometrical observations made at various hours of three days, our 

 elevation above the plain was 300 feet, and above the level of the sea 930 feet. 



Between us and the spur next on the north, there is a narrow valley having a 

 broad band of verdure on each side of the dry water-course, already mentioned. 

 To the north the view extended over a nearly level plain as far as the mountain 

 pass beyond Naupe. Northwest and west, there are lofty, isolated hills, mostly of 

 bare and precipitous rock, and west of them again, perhaps ten miles distant, are 

 the lower broken ranges of the coast mountains. To the south the view was inter- 

 rupted at a short distance, partly by hills similar to the western ones and partly by 

 the spur we were encamped upon. 



From a mean of meridian and circum-meridian altitudes of a Lyrcc, a Cygni, and 

 a Gruis, made at camp on the nights of 5th and 6th September, with sextant and 

 artificial horizon, its latitude was found to be S. 6° 0' 2". That of Olmos, from 

 similar observations of the same stars on the night of the 8th September, S. 5° 59' 20". 

 Applying to the latter the difference of latitude (42"), we have — accidentally — a 

 result varying only 0".l from the former, whilst some of the individual determina- 

 tions differ more than 40". I adopt for the station 



Latitute 6° 0' 2" south. 



On the local map, previously referred to, and which purports to have been com- 

 piled from Humboldt, Fitzroy, and others, the longitude of Olmos west of Green- 

 wich is 80° 22' 20". On the map of Arrowsraith (London, May, 1839), made up 

 in part from Capt. Fitzroy's labors, and which accompanies his narrative, it is in 

 80° 4' 30". Neither Humboldt nor Fitzroy ever visited the interior of this portion 

 of Peru, nor can I learn that its geographical position on the maps rests upon any 

 better determinations than the estimations of native travellers between it and 

 Lambayeque, not one of whom — most probably — possessed even a pocket compass. 

 Unless the line of the Andes is placed on both maps very far out of the way, 

 the longitude given by Arrowsmith is much the nearer to the truth. But, I shall 

 proceed to show that this, as well as the whole coast of South America north of 

 Valparaiso, is probably laid down by Capt. Fitzroy too far to the westward. 



The longitude of Santiago de Chile, deduced from all the moon culminations and 

 occultations observed by the U. S. Astronomical Expedition (vol. III. p. 1), during 

 the years 1849— '52, is W. 4" 42" 33^81 (70° 38' 27".l), and the difference of 

 longitude between the observatory there and that of Mr. Mouatt, at Valparaiso, 

 was found by exchanging 100 telegraphic signals — (50 in each direction) — to be 

 3"° 56'.51 (59' 7".65), Consequently, the longitude of Valparaiso would be 70° 

 37' 35". 



