520 
The Account of a 
Hence, in the spheroidical triangle DPB, we have the angles 
P D B and P B D given. 
Again, in fig. 2. let PGM be the meridian of Greenwich; 
then, if MB be the parallel to the perpendicular at G, Green- 
wich, we shall get (by Sect. vi. Art. 11.) MB = 58848 feet, and 
GM = 269328 feet ; therefore, taking 60851 fathoms for the 
length of the degree on the meridian, as derived from the dif- 
ference of latitude between Greenwich and Paris, applied to 
the measured arc (see Phil. Trans. Vol. LXXX.) we get 
G M = 44' i5 // ,26 ; consequently the latitude of the point M, 
(that of Greenwich being 51 0 28' 40"), is 50° 44' 24", 74 ; and 
the co-lat. PM = 39 0 15' 35", 26. 
With respect to the value of the arc M B, for the present 
purpose, it is not of consequence on what hypothesis it be ob- 
tained ; but if 61173 fathoms be assumed for the length of a 
degree of a great circle perpendicular to the meridian at M, 
then M B == 9' 37", 19, and the latitude of B, or Beachy Head, 
will be found = 50° 44' 2 3", 7 1. 
Again; in fig. 3. let WB be the arc of a great circle per- 
pendicular to the meridian of Beachy Head at B, meeting 
that of Dunnose in W ; anc J let D R be another arc of a great 
circle perpendicular to the meridian of Dunnose in D, meet- 
ing that of Beachy Head in R ; then we shall have two small 
spheroidical triangles WBD and RDB having in each two 
angles given, namely, WDB = 8i° 56' 53", and WB D = 
6° 55' 58" in the triangle WBD; and DBR= 83° 4' 2", 
with B D R = 8° 3' 7" in the triangle D B R ; and these re- 
duced to the angles formed by the chords, give the following 
triangles for computation, namely. 
