80 
FIFTH REPORT -1835. 
The relations which these several quantities bear to each other, 
and the deduction, when they are known, of the angles which 
Fig. 3. 
the horizontal needle will make with the geographical meridian, 
and the needle freely suspended (the dipping-needle, for example) 
with the horizon of a place, are shown in the first six problems 
of this chapter. Problems 7 and 8 contain the deduction of the 
dip, variation, and force at any given point of the surface of a 
sphere which has two such magnetic axes, the geographical po¬ 
sitions of which are known, as well as the proportion between 
their absolute forces. The 9th and 10 th problems show the 
method of deducing the proportion between the absolute forces of 
the axes, when the situation and length of the axes are known, 
and either the dip or the variation is observed. 
The expressions by which the values may be found of the 
