SOLAR-DIURNAL VARIATION OF THE DECLINATION. 499 



2 west; and at Point Barrow, where it is 41 east; 

 at all these places the westerly extreme takes place 

 within a few minutes of 1 P. M., and the easterly extreme 

 between 7 and 8 A.M., although the extreme difference in 

 the declination is 70, which is equivalent to a difference 

 of between four and five hours in the magnetic azimuth 

 of the sun at 1 p. M. From the great distances apart of 

 these four stations it may not be unreasonable to infer, 

 that the turning hours in which they all agree may be 

 found to be approximately the same, (apart from the 

 effects of the occasional disturbances), throughout the 

 middle latitudes of the northern hemisphere. When we 

 examine the corresponding phenomena of the southern 

 hemisphere, however, we find a remarkable difference 

 in the turning hours of the middle latitudes, which 

 (though not inconsistent with what is stated in the 

 earlier part of this note, viz. that the hours in both 

 hemispheres are nearly similar) seems to indicate a 

 systematic hemispherical difference of fully an hour and 

 a half in the times of occurrence both of the forenoon 

 and afternoon extremes. Hobarton is the station, in the 

 southern hemisphere, where the hours of extreme de- 

 flection have been most securely ascertained, on the 

 extensive basis of eight years of hourly observations. 

 These have given between 9 and 10 A.M. for the time 

 of the forenoon extreme, and between 2 and 3 P.M. for 

 that of the afternoon extreme. The turning hours ob- 

 served by Sir James Ross in his Antarctic Expedition, at 

 the Auckland Islands, at New Zealand, and at Sydney 

 are in accordance with those at Hobarton. Although 

 the hourly observations at Sir James Ross's three stations 

 were continued but for a few weeks at each, the results 



