492 
The Account of a 
» / n 
At Chanctonbury Ring - - 157 59 36,29 
Rook's Hill ' - - - 14 17 58,32 
Beachy Head - - - 7 42 26,56 
And the angles formed by the chords - 157 59 2744, 
14 18 3,44 
7 42 29,12 
The respective differences are in the fourth column (triang. 
xxxix.) In like manner the other differences in the same 
column have been obtained. 
We have given the results to the second place in decimals, 
though perhaps they are true only to the nearest ~ of a second. 
In finding the angles formed by the chords, we have used 
Rheticus's large Triangular Canon, where the natural sines 
are given to every 10" of the quadrant, and computed to the 
radius looocoooooo. 
It is remarked, that great accuracy in the values of the sides 
in the degrees, &c. is not necessary, and that this is true will 
be found on examination ; for in the foregoing example, if the 
sides of the triangle be varied, so that the resulting angles are 
several minutes different from those found above, still the dif- 
ferences between the spherical and plane triangles will be very 
nearly the same. 
When the three angles of any triangle appear to have been 
observed correctly, by their sum being equal to 180 degrees 
plus the computed excess, the corrections for the chord angles 
have been added to, or taken from them, as that correction 
has been negative or affirmative, and the triangle rendered fit 
for computation. Also, if in any triangle, where the sum has 
either fallen short of, or exceeded 180 degrees plus the com- 
