OBSERVATIONS. 71 



good. I was disappointed, however, from not having any observations at other stations, with 

 which to compare my own. The only place from which proper observations could have been 

 expected was Santiago; and you are aware Dr. Moesta, the chief of the observatory at that 

 city, was away for the purpose of making observations in Peru, where the eclipse was central. 

 Moreover, the eclipse was very partial in Mendoza ; and the result differs so much from the 

 determination by chronometer, that I have not hesitated to reject it. 



I have also rejected the observations of lunar distances in Mendoza and elsewhere. So far 

 as my experience goes, they are, at best, only approximations; and where, as in this case, it 

 was necessary to calculate the altitudes — thereby introducing another source of error — less 

 dependence is to be placed on them. 



I was unable to observe any occultations on either journey. When the star to be occulted 

 was of sufficient magnitude to be observed with my ship's spy-glass, clouds intervened. 



The positions of Santiago^ Eosario, Buenos Ayres, and Montevideo, are not by my determina- 

 tions ; the first being by the "Expedition," and the rest from the best English authorities. 



The longitude of Mendoza, by the observation of the end of the eclipse, is 4A. 35m. 04s. 



ELEVATION ABOVE THE SEA-LEVEL. 



In these calculations, which have been made by the formula published by the Smithsonian 

 Institute, it was necessary to assume a base; and for want of better I adopted Santiago, taking 

 the mean of all observations at 9 A. m., noon, and 3 p. M., for the months of November and 

 December, during which two months my journeys were made. Supposing the mean height of 

 the barometer at the level of the sea, in Valparaiso, to be 30 inches, and the temperature the 

 same as in Santiago, the corresponding difference of level is 1, 193 feet; which I have applied to 

 the calculated elevations above Santiago to obtain elevations above the sea-level. The only 

 exceptions to this in the table are at Eosario, Acorocorto, and Tupungato. The difference of 

 level between Eosario and Buenos Ayres is given by a comparison of all observations made in 

 each place. 



Acorocorto is so near the level of Santiago that there is doubt whether one of the temperature 

 corrections is positive or negative ; and I have, therefore, worked from assumed readings at 

 Valparaiso. The height of Tupungato is calculated from a vertical angle measured from la 

 Punta de las Vacas. 



A glance at the table of heights will show the amount of reliability to be placed on them. 

 In all places near the level of the sea the ordinary fluctuation of the barometer renders deter- 

 minations of but little value. At the Villa de la Concepcion, for instance, the observations of 

 the 16th of November give an elevation of 1,696 feet, and that at noon of the ITth gives 1,369 

 feet. For a proper understanding of the records in the column marked aneroid, it is necessary 

 to state that on my departure from Santiago, in November, 1852, I had an aneroid, which I 

 broke accidentally on mounting my horse the first day out. On the second trip I had another, 

 which was compared daily, at Eosario and Buenos Ayres, with the mercurial barometer, and 

 was not altered till I reached San Luis, where, from dampness or other cause, the dial, which 

 was of pasteboard^ had expanded so as to impede the motion of the index. It was necessary, 

 therefore^ to cut out the central part to allow free motion to the index, and probably in so doing 

 the reading was altered. After obtaining careful comparisons in Mendoza, I left for Santiago 

 by the Portillo Pass, and made corresponding observations with the syphon barometer as far as 

 the eastern Portillo, where the final lever, h, (see figure,) had reached a horizontal position ; and 

 as it was not possible to wind up the chain, of course the barometer ceased to act. On the second 

 trip from Mendoza I turned one of the screws d of the leverage apparatus e, until the lever was 

 thrown back as far as possible. Though this gave it greater range for diminished atmospheric 

 pressure, and I passed over the Uspallata Pass without having it cease to act, it was also without 

 accurate measures ; and, moreover, when I descended to near the level of the sea the lever was 

 resting against the side of the case, and the barometer could rise no farther. 



