232 



Dr. B. Stewart on Observations of Dip 



[Mar. 3, 



zontal Force made at Kew for the six years ending March 18G3. In the 

 present communication it is proposed to reduce in a similar manner the 

 results of the following six years. 



The mode of observation has already been so fully described by Sir E. 

 Sabine that no further account of it is necessary ; suffice it to say that 

 in October 1863 Mr. Chambers left the Observatory for India, and that 

 Mr. George Whipple took his place as Magnetical Assistant. Mr. Whipple 

 has since continued to observe every month with the utmost care and 

 assiduity, employing the same instruments that were used by his prede- 

 cessor, and the same methods of observation and reduction. A smaller 

 number of observations by other instruments and other observers have 

 likewise been made, but it has been thought desirable to limit this discus- 

 sion to the series made by the regular observer. I ought likewise to state 

 that both the dip-circle and unifilar stood in need of slight repairs, and 

 that they were put into the hands of opticians for this purpose ; the first 

 observation with the repaired dip-circle being that of January 1869, and 

 with the repaired unifilar that of December 1868. 



I. Dip. 



2. In Table I. we have a record of the observed values of dip made 

 with circle No. 33 by Barrow, each observation being the mean of two 

 made with the two needles belonging to that circle. 



Table I. — Observed values of the Magnetic Dip at Kew. 





1863. 



1864. 



1865. 



1866. 



1867. 



1868. 



Mean of 

 6 years. 



May 



September 



O / 



68 15-1 



II'O 

 IO'I 



io-8 

 14-6 

 68 13-2 



68 9-4 

 87 



IO'I 



io-8 

 96 

 68 ico 



68 77 

 6-6 

 9-8 

 io*o 



9"4 

 68 io-i 



68 5-8 



S'9 

 4-8 



4'9 

 4-0 

 68 7-0 



0 / 

 68 3 8 

 2-9 



2-6 

 r8 

 68 0-2 



68 3'4 

 i*i 

 11 

 18 



*9 

 68 3-4 



0 / 

 68 7 '53 

 6*03 



6-37 

 682 

 6-88 

 68 7-32 





68 12-47 



68 977 



68 8-93 



68 5-40 



68 2*27 68 2-12 



68 6-83 







1863-64. 



1864-65. 



1865-66. 



1866-67. 



1867-68. 



1868-69. 



Mean of 

 6 years. 





0 / 



68 u-8 

 118 

 Ira 

 io - 3 

 107 



68 9-9 



68 iro 



8- 5 

 96 



9 - 5 

 7-1 



68 7-4 



0 / 



63- 9 9 

 89 

 7*5 

 7'4 

 77 



68 7 -o 



0 / 

 68 6-5 

 7-8 

 4-2 

 65 



4"i 

 68 3-8 



6°8 2-8 



2-9 



3i 



27 

 68 07 



0 / 

 68 5-6 



67 59-9 

 [68 o-8j 



68 r8 

 2-8 



68 2-0 



6°8 7'93 

 7-08 

 6-03 

 6-43 



5-85 

 68 5-14 





68 10-95 



68 8-85 



68 8-07 



68 5-48 



68 2-97 



68 2-15 



68 6*41 



68 11 71 



68 9-31 



68 8-50 



68 5-44 



.68 2-62 



68 213 



68 6 62 



The number within brackets is interpolated. 



