OBSERVATIONS OF THE MAGNETIC FORCE. 
291 
“ Experiments of Deflection . — If the lengths of the magnets are in the proportion of 
1 to T224, each observed angle of deflection furnishes an approximate value of the 
77t 7Yt 
ratio -jr- by the formula -^-= ; but as in the great majority of these ob- 
servations, the value resulting from the larger distances is greater than that given 
by the lesser distances, it appears that the correction depending on the distribution 
of free magnetism in the deflected and suspended bars was not wholly inappreciable. 
The approximate results have therefore been divided by the coefficient 
the values of the constant P having been derived for each bar from observations at 
two distances of deflection by the approximate formula P = 
rV 5 sin v! — r n r h sin u 
r' b s\nu' — r 6 sin u 
These values of P are contained in Table XXXII., in which the values deduced from 
the observed angles of deflection at some of the latter stations of observation have 
been included, as well as those resulting from observations made for the purpose at 
Toronto. 
Table XXXII . — Values of P. 
Date. 
Station. 
No. 30. 
No. 31. 
No. 17. 
1844. September 25. 
29 - 
October 11. 
November 4. 
1845. January and J 
February . . ] 
Rat Portage . . 
Fort Francis . . 
Fort William . . 
Sault St. Mary.. 
Toronto 
— ’0054 
-•0076 
-•0011 
-•0019 
-•0063 
-•0068 
-•0060 
-•0038 
—•0052 
-•0034 
-•0063 
-•0035 
-•0045 
+ •0010 
+ •0004 
+ •0026 
+ •0026 
Toronto 
Toronto 
Toronto 
Means. . . . 
—•0048 
-•0048 
+ •0016 
£C The angle of deflection was first observed with the deflecting bar to the east of 
the suspended magnet, and then to the west ; four reversals were commonly made 
in each position with bars 30 and 31, and five with bar 17, which was employed at 
one distance only ; the mean angle is given in the general table ; an intermediate 
distance was employed at Fort Simpson, viz. IT 757 foot for each of the two bars, 
30 and 31 ; the distances employed at all the other stations, including those for the 
spare bars 20, 23 and 29, and for the bars 30, 31 and 17, in the experiments at 
Toronto in January and March 1845, are contained in the following Table: 
