684 



MR J. A. BROUN ON THE DIURNAL VARIATIONS OF THE 



case between 8°|- N., and 1°^ N. The St Helena curve resembles the inverse 

 curve for Simla and Madras in March. 



October. — The opposition of the curves for the two hemispheres begins to 

 show itself again nearly as in the curve for April, the Singapore curve for that 

 month resembling the Trevandrum curve for October. The passage from one 

 form to the other is not shown in the same way, nor with the same distinctness, 

 as in March. 



November and December. — The curves for these months resemble, generally, 

 those for January and February, the minimum at noon in the Indian curves 

 not being so well marked in December as in the months of November and 

 January. In the winter months the minimum occurs latest at Toronto, which 

 has the highest magnetic latitude. 



Ranges of the Diurnal Variations of the Free Needle. 



In order to compare the arcs within which the movements of the free needle 

 are performed at the different stations, the following table has been prepared :* — 



Table IV. — Ranges of the Mean Diurnal Variations of the Needle freely suspended in the direction 



of the Magnetic Inclination. 



Months. 



Maker- 

 stoun. 



Toronto. 



Simla. 



Bombay. 



Madras. 



Trevan- 

 drum. 



Singapore. 



St Helena. 



Cape of 

 Good Hope. 



Hobarton. 



January, 



1-85 



1-49 



1'22 



1-73 



1-63 



2-06 



2-64 



3-45 



3-08 



4'05 



February, 



2-25 



1-54 



1-16 



1-39 



0-96 



1-48 



2-89 



4-81 



4-56 



4-28 



March, . 



2-94 



2-30 



2-69 



2-57 



2-36 



0-79 



1-67 



4-57 



4-35 



3-30 



April, . . 



3-56 



2-48 



3-88 



4-07 



3-71 



1-67 



1-13 



3-06 



2-80 



2-60 



May, . . 



3-48 



3-03 



4-27 



4-72 



4-69 



2-90 



2-24 



2-45 



2-34 



1-56 



June, . 



3-67 



3-08 



4-37 



4-69 



4-77 



3-06 



1-83 



3-00 



1-93 



1-28 



July, . . 



3-35 



3-05 



3-90 



4-39 



4-57 



3-06 



1-94 



3-17 



1-99 



1-36 



August, . 



3-42 



3-48 



4-36 



5-42 



4-75 



3-64 



2-60 



3-32 



2-75 



1-87 



September, 



3-30 



2-51 



3-99 



5-38 



5-28 



3-31 



2-07 



2*22 



2-56 



2-65 



October, . 



3-01 



1-74 



2-36 



259 



2-37 



1-27 



2-38 



4-11 



3-55 



3-80 



November, 



239 



1-58 



0-98 



0-90 



1-50 



2-14 



2-97 



3-75 



3-81 



4-08 



December, 



1-91 



1-33 



0-78 



1-16 



1-17 



2-33 



2-90 



3-28 



3-26 



4-13 



Mean, . 



2-93 



2-30 



2-83 



3-25 



3-14 



2-31 



2-35 



3-42 



3-08 



2-91 



Minimum Ranges. 

 From this table it appears that the minimum movement of the free needle, be- 

 tween the latitudes of 56° N. and 43° S., occurs in January at Simla ; it descends to 

 Madras in February, to Trevandrum in March, and to Singapore in April. In May, 

 June, July, and August, the minimum movement occurs at Hobarton (or perhaps 

 between Hobarton and the Cape) ; in September at Singapore, or between Singa- 



* The values in the table are taken from the reduced hourly observations, and not from the 

 curves, which would give the ranges slightly greater in some cases. 



