MAGNETIC DECLINATION NEAR THE MAGNETIC EQUATOR. 683 



opposition betwixt the two hemispheres is well seen. The northern curves have 

 the maximum betwixt 8 and 9 a.m., and the minimum near 1 p.m. The southern 

 curves have the minimum betwixt 9 to 10 a.m., and the maximum betwixt 1 and 

 2 h 30 m p.m.; noon at St Helena in April. The passage from one form to another 

 is shown at Trevandrum in March, and at Singapore in April. At St Helena, 

 also, a change has begun, which throws the maximum to noon. The maximum 

 and minimum in the highest north latitudes occur about one hour earlier than 

 the minimum and maximum at the stations farthest south. The passage from 

 the northern to the southern form does not appear in these months to take place 

 by a sliding shift of the epochs ; at Trevandrum the curve for March approaches 

 the straight line, and is very nearly that which might have been derived from 

 the mean of the curves for Madras and Singapore in the same month. 



May, June, July, and August. — These months may be considered together, as 

 the comparison gives nearly the same conclusions. The first remark is, that 

 when the sun is farthest north, there is really no inversion of the law of move- 

 ment betwixt the latitudes of 56° N. and 43° S. The movements are, with slight 

 exceptions, as follow : — The north end of the needle moves eastward from after 

 midnight till near 7 a.m., it then turns westward, attaining the extreme westerly 

 position at from l h to 10 h 30 m or IP p.m., the former hour farthest north, the latter 

 farthest south, and near noon at the equator. The north end of the needle then 

 moves eastwards till from 3 to 6 p.m., the latter hour at the northern stations, 

 the former at the southern, and near 4 h 30 m p.m. at the equator. The north end 

 then moves westerly for a short period at all the stations, from Simla southwards, 

 or continues slowly eastwards at the most northern stations. From about 

 8 p.m. the movement is easterly at all the stations, excepting Hobarton, where 

 the easterly movement does not commence till near midnight. 



In general, the curves for these months show a slight shift of the epoch of 

 minimum, and at Hobarton the afternoon maximum becomes the principal one ; 

 but there is no inversal of the law of movement. 



The curves for St Helena show a curious movement near noon, which appears 

 in some degree the equivalent of the movement at Simla, Bombay, and Madras, 

 in November to February. Thus, at St Helena, in May, June, July, and August, 

 there is the maximum at 7 a.m., a minimum at 10 a.m., a maximum at noon to 

 3 p.m., and minimum at 5 p.m.; while at Bombay, &c, in November, December, 

 January, and February, there is the minimum at 7 a.m., a maximum at 9 h 30 m a.m., 

 a minimum at noon, and maximum at 4 p.m. It seems probable that at some 

 station betwixt St Helena and the equator this resemblance of opposition would 

 be better shown. 



September. — In this month the minimum, which occurs betwixt noon and 1 

 p.m., from Trevandrum northwards shifts suddenly to 10 a.m. at Singapore, at 

 which hour it occurs at all the southern stations, so that the shift occurs in this 



