18 



MAGNETICAL OBSERVATIONS. 



OBSERVATIONS AT ORIZABA. 



Description of Station No. III. — The instruments Averc mounted under a roof 

 of palm leaves, in the garden of Mr. Thomas Grandison, at Cocolapam, about a 

 thousand yards to the south of the town of Orizaba. A few hundred yards west 

 of the magnetic station rises a huge mountain ridge, of ancient volcanic rock, to 

 a height of 1,500 to 2,000 feet above the plain. This may possibly cause some 

 small local disturbance. 



\ The elevation of the station above the level of the sea was found by barometrical 

 observations 4,042 English feet. 



In the determination of absolute declination a break in a distant mountain ridge 

 to the eastward was used as a mark (A). 



No experiments of deflection have been made at Orizaba. 



Station No. III. Cocolapam near Orizaba. 

 Latitude 18° 53'. Longitude 97° 4' W. of Greenwich. 



