306 Transactions of the South African Philosophical Society. 



§4. Easterly and Northerly Components. 



By the differentiation of the ordinary trigonometrical relation 

 between Easterly Component, Horizontal Intensity, and Declination, 

 and between Northerly Component, Horizontal Intensity, and 

 Declination, we have — 



AY = AH sin D + H cos DAD 

 AX = AH cos D - H sin DAD. 



A monthly mean value of D can be calculated from the records 

 published by Beattie and Morrison in the Transactions of the 

 South African Philosophical Society. We have then sufficient 

 data for obtaining the daily inequality of the Easterly and the 

 Northerly Components (Tables VII. and X.). 

 Again we have — 



A'Y = A'H sin D + H cos D A'D 

 A'X = A'H cos D - H sin D A'D 



with two equations of a similar nature for A"Y and A"X. 



TABLE VII. 

 AY. 



Unit ly. 



Cape of 



Good Hope 



Hours 



I. 



II. 



III. 



IV. 



V. 



VI. 



VII. 



VIII. 



IX. 



X. 



XI. 



XII. 



(Astro- 

 nomical). 



























§ +34min. 



& ° 

 1 



4-4 



1-0 



2-4 



2-7 



— 2-1 



— 4-3 



— 5 



7— 6-9 



— 2-9 



4-5 



1-2 



4-9 



8-3 



9-7 



9-3 



7-0 



— -4 



— 1-6 



— 3 



2— 4-4 



— -2 



12-1 



7 



8 



9-3 



2 



10-1 



14-7 



12-7 



6-5 



•8 



•7 



1 



1— -3 



1-6 



12-9 



10 



3 



8-3 



3 



7-2 



13-2 



10-8 



4-7 



2-2 



1-4 



2 



7 1-6 



1-6 



9-5 



9 



1 



5-8 



4 



5-8 



8-5 



6-4 



3-2 



•1 



1-4 



— 3 



4 -9 







1-0 



5 



6 



3-6 



5 



4-1 



4-7 



3-4 



1-2 



— -9 



— -9 



— 1 



8— 2-4 



— 1-8 



— -8 



2 



3 



2-2 



6 



1-9 



1-8 



1-3 



— 1-5 



— 1-0 



— 1-8 



— 3 



1— 3-1 



— 3-4 



— -6 



2 







1-4 



7 



2-0 



2-3 



— -1 



— -9 



— 1-5 



— 3-7 



— 4 



7— 3-7 



— 2-9 



— -5 



2 



3 



1-8 



8 



3-0 



1-8 



•3 



— 1-1 



— 2-8 



— 3-5 



— 3 



9— 3-3 



— 3-0 



1-1 



4 







2-2 



9 



1-5 



2-5 



•9 



- 1-0 



— 2-1 



— 3-6 



— 4 



5— 2-8 



— 3-5 



1-2 



4 



5 



2-9 



10 



2-5 



2-8 



•5 



— -3 



— 1-0 



— 3-6 



— 3 



6— 2-8 



— 1-7 



1-5 



4 



3 



3-5 



11 



1-6 



2-0 



2-0 



•7 



— 1-7 



— 2-0 



— 2 



2— 1-9 



— 1-0 



2-0 



5 



2 



4-1 



12 



1-8 



3-6 



2-2 



— -8 



— -3 



— 1-6 



— 



7— -7 



— -1 



2-1 



5 



4 



3-3 



13 



•5 



2-8 



4-1 



3-2 



1-0 



•1 





8 -4 



1-7 



2-8 



3 



6 



2-8 



14 







1-8 



4-3 



3-8 



•9 







1 



8 1-4 



2-0 



1-8 



3 



5 



2-3 



15 



— -3 



2-9 



3-6 



3-9 



2-0 



1*6 



1 



•8 3-2 



2-1 



1-4 



1 



9 







16 



— 1-6 



2-3 



3-6 



4-1 



3-0 



1-8 



2 



•3 3-9 



2-1 



1-0 





6 



- '9 



17 



— 2-6 



1-8 



3-0 



5-1 



3-5 



2-0 



2 



•8 4-7 



3-0 



•1 



— 1 



G 



— 3-9 



18 



— 4-8 



1-3 



1-7 



5-2 



6-9 



5-0 



5 



•0 8-8 



9-8 



— 1-6 



— 6 



2 



— 8-3 



19 



— 8-4 



— 5-7 



— 4-5 



2-1 



11-5 



10-4 



10 



■8 13-1 



12-8 



— 8-3 



—11 



2 



—13-2 



20 



—11-4 



—17-1 



—15-5 



— 8-3 



2-8 



5-3 



10 



•1 6-7 



5-1 



—15-9 



—19 



G 



— 13-3 



21 



—12-9 



—24-6 



—22-5 



—15-6 



— 4-4 



1-5 



1 



9 1-1 



— 2-3 



—15-9 



—19 



5 



— 11-9 



22 



—2-6 



—22-5 



—18-9 



—15-0 



— 9-1 



— 3-7 



— 3 



9— 6-2 



— 8-3 



—11-7 



—11 



4 



— 6-2 



23 



-2-8 



—11-7 



— 8-5 



— 5-8 



- 7-2 



— 5-4 



— 6 



7— 9-6 



— 8-8 



— 3-2 



— 4-6 



-- -4 



