90 Staff-Commander E. W. Creak. [Jan. 28, 



St. Helena. 





Declination. 



Inclination. 



Total force. 



Observer. 



Longwood Magnetic 



22 c 



48' W. 



21° 



21-7' SL 



6-030 



Observatory 



Observatory 













results. 







- { 



18 

 20 



16 



3 



6'287 







19 



38 









Ross, 1840. 



At the anchorage .... 



22 



17 



17 



55 





Dupetit Thou- 













ars, 1839. 





22 



53 



18 



37 



6-075 



Ross, 1840. 



At Longwood Magnetic Observatory the declination is apparently 

 undisturbed, whilst in the Castle Gardens it differs 3j° from the 

 normal value. The inclination at Longwood differs 2J° from the 

 normal, pointing to the presence of an excess of red magnetism in that 

 locality. The total force is not much disturbed. 



At Sister's Walk the inclination at two stations, 50 yards apart, 

 differs if", one being in excess of the normal by If ° nearly, the other 

 twenty minutes in defect ; the larger disturbance being due to red 

 magnetism. The total force is increased as much as 0*2. 



The result of the inclination by Dupetit Thouars, which is 42' 

 below the value derived from Ross's observations, seems to indicate 

 that a lower value might be accepted as the normal. 



Tristan d'Acunha.. 





Declination. 



Inclination. 



Total force. 



Observer. 



Near Julia Point .... 



23° 5'W. 

 21 15 



40° 40' S. 

 41 42 



~Not observed 

 6-36 



H.M.S. "Chal- 

 lenger," 1873. 





The observing station at this island was situated on the ET.W. coast 

 near some cliffs extending to the eastward. The westerly declination 

 is increased about If above the normal,, but as the inclination is 

 slightly affected by blue magnetism, it is uncertain whether it is the 

 red magnetism in the adjacent cliffs to the eastward repelling the red 

 end of the compass needle, or the blue magnetism near it which causes 

 the increase of the declination. 



* At Sister's Walk, Crozier's observing station was 50 yards S.S.E. of Ross' station. 

 The dip circles were interchanged at the time to prove the difference observed was 

 not due to instrumental error. 



