16 



MAGNETIC OBSERVATIONS MADE AT PANAMA. 



Mr. Bond and Mr. Whipple at the magnetic observatory at Cambridge made ob- 

 servations with the same instrument upon needles A, B, and C, and the following 

 are some of the results obtained : — 



1849, February 24th. Temperature 42°, magnetic inclination by needle B, . 

 Angle of deflection of needle J5, with deflector north at apparent dip, 



" " " " south " ... 



Feb. 24th. Temperature 46°, angle of deflection of needle B with weight 2 grs., 



" " 2 -f 1 grs.. 



Feb. 25th. 



36.5, 



2 + 1 + 5 grs. 

 2 grs., 

 2 + 1 grs., 

 2-f 1+0.5 grs 



74° 33 .9 

 32° 55.6 

 34° 04 



23 32.25 

 36 28.75 



,44 05.3 

 23 26.55 

 36 25.65 



,43 55.25 



Plane of instrument in magneiic meridian, magnetic declination 9° 28' west. 



Formula for Computation, I' 



I sin V 



I = Intensity of magnetism of the needle at Cambridge, Mass. 



V = Angle of deflection 



V r= " " " " station, 

 r nr Intensity of magnetic needle at station. 



Results for Magnetic Intensity. Obtained hy Computation of the Preceding Observations. 



Results for intensity at Panama, 0.87507 

 " " Gorgona, 0.87229 



" " Chagres, 0.87493 



