XXVi GENERAL RESULTS OF THE MAGNETICAL OBSERVATIONS. 
TasBLE 7.—Horizontal Force—Correction for Mean of Observation Hours 
in Seale Divisions. 
20%, 23%, . 
20%, 23%, 2h, 5B, 
Month. 2h, 5b, Bh, eee a G. M. 7. 
G. M.T. See 
Before After 
July 8, 1851. July 8, 1851. 


January, —1:01 —1:10 
February, . —0°05 — 0-06 
March, + 0:99 + 1:07 
April, +301 + 3°27 
May, +2:90 +3:15 
June, + 3°53 + 3°84 
July, +361 +3°92 
August, +3°30 +358 
September, +3°45 +3°75 
October, +1:98 +2°15 
November, +0°77 + 0:84 
December, 
—0:05 — 0°06 

If the corrections recorded in this Table be applied to the observations, we obtain 
the monthly means as follows :— 
TaBLE 8.—Horizontal Force—Monthly Means in Scale Readings. 
















Month. 1847 _ 1848 1849 1850 1851 1852 1853 1854 1855 
January, . | 558-69 | 557°74 | 568°61 | 584°75 | 593:23 | 610-54 | 626°35 | 638-21 | 652.35 
February, . | 556-10 | 556-59 | 571°19 | 584-63 | 593-77 | 612-04 | 626-11 | 637°95 | 651-01 
March, . . | 557-82 | 559-88 | 571°36 | 582-46 | 597-93 | 610-26 | 625°50 | 640-12 | 640°77 

April, . . | 557-26 | 562-23 | 574:56 | 587-58 | 601°95 | 615°57 | 629-26 | ....... 651-10 
May,. . . | 557:44 | 567-03 | 580°20 | 589-45 | 600-52 | 618-03 | 631°73 | ...... 651-50 
June, . . | 562-63 | 568-98 | 586°84 | 591-21 | 603-63 | 620-99 | 631°86 | ...... 65302 
July, . . | 560-34 | 568-88 | 584-10 | 590-13 |*610-°56 | 619°64 | 632-55 } ...... 649-29 
August, . . | 559-37 | 567-49 | 580:87 | 589-22 | 607:90 | 619-31 | 634-20 | 11... | esses 
September, . | 558-19 | 564:29 | 578°85 | 588-27 | 600°13 | 618-56 | 63090 | 647-32 | «.---- 
October, . | 551-71 | 568°35 | 578-04 | 588-46 | 602-40 | 618-41 | 635-56 | 659-05 | 653-29 
November, . | 556:17 | 566:85 | 581-23 | 592°88 | 611-17 | 620°53 | 637-42 | ...... 657:04 
December, . | 563-65 | 566°72 | 584°78 | 595°63 | 611°78 | 623°68 | 638-77 | 628-41 ‘ 

* After June 1851 the new value of the scale reading commences (see Introduction, page xiv.) 
If we obtain the mean scale reading for each year by taking the mean of the 
months in the above Table, and if we then reduce these yearly means to parts of 
force and compare consecutive years together, we shall obtain values for the ap- 
parent secular change of horizontal foree—apparent only, because the lengthening 
of the thread and loss of magnetism of the magnet will cause gradual change in the 

