Trigonometrical Survey. 
433 
Reduction of the Base to the Temperature of 6 2°. 
Apparent length, namely, 274 chains -f- 1 ,755 Feet, 
feet - - - 27401,755 
The correction for the excess of the chains 
lengths* above 100 feet, and half their wear, is 
05489 . and this add . . 2i05g9 
The sum of all the degrees shewn by the ther- 
mometers was 96795,25; therefore 9 6 79S’ 2 S — ^ 
x 274 x ’-—i is the correction for the mean heat in 
which the base was measured, above 54*, the tern- 
perature in which the chains were laid off ; and 
this also add - 2,8519 
Hence these corrections, added to the apparent 
length, give - - 27406,6608 
Again, for the reduction of the base to the tern- 
8° 
perature of 6<z we have — x 3,38938 ; and this sub- 
tract 2,2596 
By the table, the sum of all the corrections for 
reducing the several hypotenuses to the plane of 
the horizon is 1,02867 inches = 0,08572 feet ; and 
this subtract - - 0,0857 
Hence these corrections taken from the above 
length leaves that of the base in the temperature 
of 62° - - - - 27404,3155 
For the lengths of the chains A and B see art. vii. of this section. 
