MAGNETIC OBSERVATIONS. 9 



Valparaiso, Chile. The ship was swung in this harbor, on April 4th, 1866, in 

 the usual manner. Her position at the time was hit. 33° 2' S., long. 71° 38' \Y. 

 Joint XII on the after turret was 4.25 inches to port. While we were lying at 

 Valparaiso the ship was perfectly free to swing to the tide, and she turned in all 

 directions. 



The observations taken on shore March 2d were made on the south end of the 

 white sand beach at the Estero de Quilpuc, at a spot about two hundred and fifty 

 feet from the rocks. Assuming the position of Fort San Antonio to be lat. 33° 1' 

 53" S., long. 4" 46 m 46 8 .0 W., then, according to the English Admiralty Chart, the 

 position of this station was approximately 



Lat. 33° T.4 S. 

 Long. 4 h 46 ra 31 s W. 



The observations of March 19th, and all taken subsequently to that date, were 

 made at a spot distant about six hundred and fifty feet, nearly true north, from the 

 most northern of the custom-houses. The instruments were set up, near to the 

 water's edge, on the public road which here runs along under a high bank of rock. 

 The true bearing of the flagstaff at Fort San Antonio, on the top of the hill, was S. 

 31° 45' W., and its estimated distance was seven hundred feet. Assuming the posi- 

 tion of the fort to be as stated above, the position occupied by the instruments is in 



Lat. 33° T 47" S. 

 Long. 4" 46 m 45\7 W. 



Both this station and that of March 2d were carefully tested for local attraction 

 by taking fore and back sights with a compass, but none could be detected. 



In adopting 4 h 46 m 46 s . as the longitude of Fort San Antonio, I have followed 

 Raper, but this value is doubtless too large. Capt. Jas. M. Gilliss, U. S. N., from a 

 series of occultations and moon culminations, observed during the years 1850-51-52, 

 determined the longitude of the Observatory on the hill of Santa Lucia, in Santiago, 

 to be 4 h 42 m 33 3 .8. Dr. Moesta, from subsequent observations up to the year 1862, 

 corrected this value to 4 h 42 m 33 3 .0. Capt. Gilliss, by means of the electric tele- 

 graph, found the difference of longitude between the Observatory at Santiago and 

 Mr. Mouatt's Observatory at Valparaiso to be 3 ra 56 s .5. Hence, adopting Dr. 

 Moesta's value of the longitude of Santiago, we have 



4 h 46 m 29\5 W. 



as the longitude of Mr. Mouatt's Observatory; but I have been unable to find any 

 description of its position, and consequently cannot refer this longitude to Fort 

 San Antonio. 



Findlay, in his "Directory to the South Pacific Ocean," edition of 1863, gives 

 for the longitude of Fort San Antonio 4" 46 m 28 8 .8, and quotes Dr. Moesta as the 

 authority. The Connaissance des Temps, for the year 1868, on the same authority- 

 gives 4" 46'" 27 s . 5 for the same position. Which of the two values is nearest cor- 

 rect I am unable to say. 



Callao, Peru. The ship was swung in this harbor, on April 29th, 1866, in the 

 usual manner. Her position at the time was lat. 12° 3' S., long. 77° 14' W. Joint 



2 December, 1871. 



