308 
GENERAL SIR EDWARD SABINE ON THE RECORDS OE THE 
date as I could have wished, and should otherwise have accomplished ; but I now present 
them as the first instalment of a research which I hope we may regard as permanently 
established and provided for by Mr. Gassiot’s munificent donation. 
The method by which the tabulated hourly records of the Horizontal and Vertical 
Forces have been separated into their two categories of disturbed and (comparatively) 
undisturbed values, was described originally in the 3rd Volume of the Magnetical Obser- 
vations at the Toronto Observatory, published in 1847, and has since been frequently 
employed and discussed in papers printed in the Philosophical Transactions and elsewhere. 
It is the same which was subsequently adopted by Dr. Alexander Dallas Bache, For. 
Member of the Royal Society, in his admirable discussion of the Results of the Magnetical 
Observations made at the Girard College Observatory in Philadelphia, in the years 1840 
to 1847 inclusive, published in the Smithsonian Contributions to Knowledge, vols. xii. 
and xiii. In the case of the hourly records of the horizontal Force at Kew between 
January 1, 1858, and December 31, 18G4, the number of instances in which the records 
indicated an amount of disturbance equalling or exceeding T50 of an inch, taken as 
the separating value, was 5932, being about 1 in 10 ; and in the case of the records of 
the Vertical Force between the 1st of January 1859 and the 31st of December 1864, 
6957, being about 1 in 7 of the whole body. The value of T50 of an inch in parts of 
the respective forces in the different years was as follows : — 
1858 .... 
Horizontal Force. 
. 0-00124 
Vertical Force. 
1859 .... 
. 0-00141 
0-000357 
1860 .... 
. 0-00152 
0-000377 
1861 .... 
. 0-00157 
0-000389 
1862 .... 
. 0-00162 
0-000381 
1863 .... 
. 0-00168 
0-000377 
1864 .... 
. 0-00174 
0-000399 
Means . 
. 0-00154 
0-000380 
Distributed into the several years of their occurrence, these showed the proportions in 
each year to be as follows : 
In the Horizontal Force. 
Year ending December 31, 1858 . 
. . . 267-893 inches. 
55 
55 
1859 . 
. . . 369-286 
55 
55 
55 
1860 . 
. . . 270-349 
55 
55 
55 
1861 . 
. . . 206-748 
55 
55 
55 
1862 . 
. . . 183-645 
55 
55 
55 
1863 . 
. . . 114-642 
55 
■55 
55 
1864 . 
. . . 114-725 
55 
Total in 
the 7 years 
. . . 1527-288 
55 
Mean Annual Value 
1527-288 
-4--- =2 18- 184 
55 
