ON THE PHENOMENA OF TERRESTRIAL MAGNETISM. 81 
several quantities treated of in these problems, collected in one 
view, are subjoined. 
In these expressions 
a = = = the arc between the ends of the magnetic 
chord and the poles of the magnetic equator. 
8 = P b F — the angle between the first magnetic meridian 
and the polar colure. 
e==NER = PZ> = the angle between the geographic and 
magnetic equators. 
£ = M P b = the geographical longitude of the north pole 
of the magnetic equator. 
Yj = L C c = the angle of the magnetic meridian with the 
horizon. 
fi = LQ = ^LCQ = the apparent magnetic latitude. 
v = EZ>L = the apparent magnetic longitude. 
= E y e = the true magnetic longitude. 
90° — u — L y R — the true magnetic latitude. 
90° — v = L c e = the eccentric magnetic latitude. 
90° — ]) = PL = the geographical colatitude. 
g = MPL = the geographical longitude reckoned east - 
ward. 
i = dLt a 1 (fig. 1.) — the oblique dip ; or the angle of the 
magnetic line of repose and the tangent to the mag¬ 
netic meridian. 
co — /fl'LM (fig. 1.). 
A — LP (fig. 3.) the angle of the magnetic vertical 
circle, and the geographical meridian of L. 
R = L c = the radius of the magnetic meridian. 
M and M' =■ the absolute forces of the two axes. 
] at a given 
m 7 f ; = r 
> place due to 
o 
II 
J one axis. 
V = 
titles due to 
the other axis, 
c = the angle of the forces of the two axes. 
~ 1 due to the compound action of the two 
~~ ., £ 1 i axes, 
K ss the force 
Formulae. 
1 . sin [x = cos e , sin p + sin s . cos p . cos (q — Q. 
2 . cot (v + 8 ) = cos e. cot (q — ?) — sin e . ta np . cosec (q — £)* 
3. cot A = cot s . cosec (q — ?) . cos p~— sin p . cot ( q —£)> 
. , . sin a 
4. cot <p =- ; -cot v. 
cos [x . sm v 
5. R = \/l + sin 2 a + 2 sin u . cos (x . cos v .* 
1835. g 
