40 



Mr. W. Ellis on the Diurnal Variations 



curves it will be seen occupy nearly similar positions, rise of 

 the horizontal- force curve being accompanied by fall of the 

 vertical -force curve; the nodal points for declination occupy an 

 intermediate position. As regards the comparative magnitude 

 of the deviations, the range (difference between the greatest 

 and least) is, for declination 1/-04 ( +0'*38 to — (K'66), or in 

 metric measure 55 ( + 20 to —35); for horizontal force, 

 metric, 31 ( + 16 to —15), and for vertical force 50 ( + 26 

 to -—24). The sums of the twenty-four hourly deviations, 



MTU 



metric, taken without regard to sign, are for declination 392, 

 for horizontal force 200, and for vertical force 398. 



It is remarked by Messrs. Bobson and Smith that the range 

 of the diurnal inequality in declination in each of the tliree 

 years 1883, 1886, and 1887 is less at Greenwich, including 

 all days, than at Kew for quiet days, by 0'*5, 0'*3, and 0'*5 

 respectively, as though magnetic irregularities tended to 

 diminish instead of increasing the diurnal range. In the fol- 

 lowing Table there is given, in addition to the diurnal range 

 (difference between greatest and least), the sums of the 

 twenty-four hourly deviations from the mean, taken without 

 regard to sign. 



