\ 
—— 
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z 
Length of a Degree of a Parallel of Latitude.. “ 
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Length of a Degree of a Parallel of Latitude. 
1. Knowing the reduction of latitude (formula (6)) and the ter- 
restrial radius (formula (7)) corresponding to any place, the length 
of a'degree of the parallel of latitude at the same place, may ‘be 
readily found as follows: The parallel being the circle generated by 
the point m, during the revolution of the generatrix, will have its 
radius equal tox: now we have already shown, that e=pcos.() — 4); 
and if we designate by /, the length of the degree sought, we shall 
have I= yap9c0s.(L—6) ; if in this we place the value of p given 
by formula (7), we sball find 
: 3.(—3) 
te S063 miles X 99 XT TT ROB TEs. won: 
2. Having first found 6, by formula (6), and then substituting the 
value of 6 thus found, in formula (8) we shall at once reduce the 
. corresponding value of 2; and it isin this manner that we have con- 
structed the following table, in which columns A exhibit the latitudes 
differing by 1°, and columns B the corresponding length of a degree 
of the parallel of latitude. 
Lengths of Degrees of Parailels of Latitude. 
= 
Se 
n 
SREGBR Bo > 
BES 
HSE ASAIAZDSS 
Should the parallel pass through a place whose latitude falls be- 
tween two consecutive ones given in the table, the length of the 
degree may be approximated to, with a sufficient degree of accuracy, 
by a method entirely similar to that explained in the subject of the 
length of a degree of the meridian; but if the utmost accuracy 
required, wien we must deduce the length of the degree from the 
formula 
