420 



Mr. J. A, Broun on the 



[June 20, 



for 26 days were found for 1844 = -20, for 1845 = — 7. The daily 

 means from the Tables * were then arranged in groups of 25f, 20, and 

 26^ days, as follows : — 



da f 1844, Jan. 1 to 1844, Dee. 29 = 14 periods. 



ayS 1 1844, Dec. 25 to 1846, Jan. 14 = 15 „ 

 da g | 1844, Jan. 1 to 1844, Dec. 29 = 14 „ 

 ayS 1 1844, Dec. 30 to 1845, Dec. 28 = 14 „ 



261 ] r J 1844 > Jan - 1 t0 1845, Jan. 3 = 14 

 3 CajS t 1845, Jan. 4 to 4846, Jan. 6 = 14 „ 



The corrections for secular change were applied to the means derived 

 from these groups, and in the calculation for 26-L days the fractional 

 part of a day in excess was omitted, while in that for the 25| days the 

 26th day of each third period served also as the 1st day of the next. The 

 resulting means are given in the following Table : — 



Mean Horizontal Force for each day in periods of 25|, 26, and 26| days, 

 as deduced from the Makerstoun Observations for 1844 and 1845. 



25i 



26 



Period. 



Year. 



L 



2. 



3. 



4. 



5. 



6. 



7. 



8. 



9. 



10. 



11. 



12. 



13 



d. 



25f { 



1844 

 1845 



99 

 243 



95 

 259 



95 

 262 



102 

 241 



101 



246 



88 

 236 



83 

 218 



84 

 210 



80 

 231 



85 

 242 



91 

 213 



70 

 227 



41 



236 



26 { 



1844 

 1845 



82 

 234 



100 

 192 



92 

 218 



98 

 227 



88 

 228 



95 

 238 



79 

 240 



90 



236 



67 

 244 



70 

 201 



59 

 198 



48 

 210 



49 

 214 



m { 



1844 

 1845 



92 

 242 



97 



249 



102 

 204 



87 

 212 



72 

 218 



81 

 221 



68 

 216 



71 



233 



68 

 243 



65 

 235 



51 

 247 



30 

 255 



55 

 242 



Period. 



Year. 



14. 



15. 



16. 



17. 



18. 



19. 



20. 



21. 



22. 



23. 



24. 



25. 



26. 



d. 



25| { 



1844 

 1845 



59 

 250 



48 

 236 



56 

 226 



64 

 234 



51 

 224 



72 

 219 



60 

 221 



69 

 223 



76 



222 



90 

 232 



108 

 237 



93 

 237 



102 



246 



26 [ 



1844 

 1845 



55 

 220 



50 

 225 



56 

 231 



69 

 241 



71 



238 



81 

 246 



87 



256 



83 

 251 



100 



230 



111 



236 



106 

 244 



107 



234 



94 

 231 



26* { 



1844 

 1845 



69 

 247 



73 

 249 



78 

 237 



82 

 221 



90 

 250 



84 

 216 



97 

 236 



104 

 231 



112 

 217 



101 



227 



95 

 245 



90 

 251 



90 

 244 



The unit = 0-000014 of the whole horizontal force. 



A constant quantity - 00300 was subtracted from the means deduced from the Tables 

 to obtain the above quantities. 



Having, as for the Greenwich means, calculated the constants for the 

 term a sin (0-hc), they were found as follows : — ■ 



* Table xxii." Makerstoun Observations, 1844, Trans. Roy. Soc. Edinb. vol. xviii. 

 p. 355 ; and Tables xviii. and Ivii. Makerstoun Observations, 1845, Trans. Roy. Soc. 

 Edinb. vol. xix. pt. 2, pp. 11, 32. 



