the Trigonometrical Operation. 22 ,, 
It bath been already remarked, that, from p. 276. Meri. 
dienne lerifiee, Dunkirk is 1430 toifes eaft ward from the me- 
ridian of- Paris; and that in p. 36. of the Defection Geome- 
trique de la France, we find it only 1416 toifes. Now, thefe 
will give 2' 22 // .6 and 2' 2i".a refpeftively for the difference 
of meridians of Dunkirk and Paris; the mean is 2' 21". 9 for 
the longitude of Dunkirk eaft from Paris ; therefore 2 0 22' 
3 -9 ~ 2 21 / -9 = 2 19' 42 // , or 9' 18A8 in time, will be the 
longitude of Paris eaft from Greenwich nearly. 
Again, in fig. 10. let P be the pole ; G Greenwich, PW its 
meridian ; RD an arc of a great circle making the angle at R 
a right one, and pafting through D ; and DW an arc of the 
parallel of latitude of Dunkirk. 
By p. 240. of the Man., de V Acad. 1758, the celeftial arc 
between Paris and the ftation of the feftor near Dunkirk is 
2°u' 50"; to which adding 5 ". 3 (-844 toifes) for what 
the tower is north from the ftation, we have 2 0 iff 55A3 for 
the arc between Paris and Dunkirk ; therefore, if the latitude 
of Paris is 48° 50' 1 4.", that of Dunkirk will be 51 0 2' 9". 2, 
whence its co-latitude becomes 38° 57'' 50 // .7 = DP. 
From what has been faid concerning fpheroidical triangles, 
it follows, by way of corollary, that to find RD by fpherical 
computation, when DP and the angle at P are given, it is 
neceffary to diminifti DP by a certain quantity determinable 
from the nature of the fpheroid ; this quantity is about 0".$ 
when the fpheroid is M. Bouguer’s; therefore DP may be 
taken = 38° 57' 50 x/ .2, which is fufficiently accurate for com- 
putation. 
Hence, as rad. : fine DP :: fine 2 0 22' $".9 - WPD : fine 
1 29 19 / . 1 7 = the arc DR. Now, 61247 fathoms being 
equal to i° of a great circle perpendicular to the meridian in 
the 
