3 
and 
ilf-2 
(360 /2t) 
r-2 “ 
2 
(360 /27r) 
“-3 — 
3 
(360 /2x) 
i-n — 
n 
and 
( 1 ) 
or, expressed in logarithms 
log Tn = log Mn — log n + [1*7581226] 1 
log r_n = log M.n — log n + [1*7581226] J 
The radius of sphere to be used for the parallel of latitude 60 degrees, 
is the meridian radius of curvature of the earth ellipsoid at that latitude 
which is found in the Smithsonian Geographical Tables, but may be calcu- 
lated by above formula, from the arc of 1 degree between latitude 59° 30' 
and latitude 60° 30'. 
TRANSFORMATION OF RECTANGULAR CO-ORDINATES 
Figure 1. 
ordinates — be represented by the line COP] the rectified arc of great 
circle 0 P', perpendicular to the central meridian at latitude 60 degrees 
to be taken as axis of abscissae with the intersection 0, as origin of co-ordi- 
nates. The arc C D P' represents the equator, and point P, the pole. 
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