of the Trigonometrical Operation . 509 
kirk for the hypothenufe, will give 89° io f/ for the angle be- 
tween the me ridian and this arc ; hence 89° 58' 10" - 88° f 34^ 
— i° 4s 7 36" is the angle at Dunkirk between the two arcs ; 
one perpendicular to the meridian of Greenwich, and the other 
to that of Paris ; therefore, if we take 1416, or 1430 toifes, as 
the leg of a plane triangle adjacent to this angle, we get 9059, 
or 0 1 4*8 \ feet, for the diftance of the meridian of Paris from 
Dunkirk on a great circle perpendicular to the meridian of 
Greenwich ; thefe taken from 547053,8 will leave 537994.8 
or <37905,3 feet, for the diftance between the meridians of 
Greenwich and Paris on that circle, according as Dunkirk is 
1416 or 1430 toifes from the meridian of Paris. 
Should it be thought more accurate to make ufe of the diftance 
between Calais and Dunkirk, according to the fcale in the 
XXXV triangle deduced from the Englifh obfervations acrofs 
the Channel, it is had at one proportion thus ; as 12077,85 
toifes (the French diftance between Blancnez and Montlam- 
bert) is to 77235 feet (the Englifh diftance) fo is 19349.34 
toifes (the French diftance of Calais and Dunkirk) to 123734,5 
feet, as in the XL triangle, which exceeds the French diftance 
about 5 feet : this will give the diftance between the meridians 
of Grenwich and Paris 4.4 feet more than the above determina- 
tion. But was the bale on Romney Marfh adhered to, it would 
give the diftance about 2 feet lefs ; and therefore the refultsof 
the French triangles on their coaft would agree nearer with the 
deductions from this bafe than from the other on Hounflow 
Heath. ' 
P. 187. in lines i. and 8. for 358.6 put 349.4 s and confe- 
quently in line 10. for 133409.8 put 133419. This error is the 
caufe of the difference in the diftances of the parallels of latitude 
of Greenwich and Paris as given in Art. to. and 13. Sed. VI. : 
