Comparisons of Magnetic Standards, 1905-14 



239 



at station A', thus making the mean times for each instrument at each intercomparison 

 practically the same. The C. I. W. dip circle used was Dover No. 206 (with its own needles 

 I and 2, and 5 and 6 of dip circle No. 178). 



'All values are referred to station A: .4 = B+2'.6. 

 Table 13 B.- Results oj Horizontal-Intensity Comparisons at the Hongkong Observatory, 1907-1911 . 



It will be noted that the result from series II differs considerably from those for series 

 I and III, wliich are in fair accord. It has not been possible to determine whether the 

 //-values with the Observatory instrument (No. 55) depend upon strictly comparable 

 constants, somewhat different constants being used from time to time. 



The large value of the correction of No. 55 as found above, viz, +0.00134//, is 

 believed to be chiefly due to the fact that in the Observatory computations the deflection 

 distances 30 and 40 cm. are assumed as ab.solutely correct at C. Curiously enough, the 

 correction of No. 55, as found from the C. I.W. comparisons, is practically the same as that 

 above cited (+0.00141//), which resulted from the comparisons in 1898 between Nos. 55 

 and 83, the constants of the latter instrument having been determined in 1897 at Kew. 

 No. 55 was purchased in 1883 and has been in use at the Observatory since about 1884. 



