6q6 The Account of a 



degrees. From these data, the latitude of the point B is easily 

 derived; for cosine 15' 10" ,g : radius : : cosine 39 36' 56", 7 : 

 cosine 39 36' 54",2, the co-latitude of B; hence 39 36' 54",2 

 + 4' 38",8 = 39 41' 33",o the co-latitude of A ; hence 50 18' 

 27" is the latitude of St. Agnes. Its longitude, west from 

 Hensbarrow, is also found by a simple proportion ; sine 39 36' 

 54",2 : radius : : sine 15' iC',9 : sine o° 23' 48"; therefore, 

 4 48' 7",7 -f o° 23' 48" = 5 ° 11' ss",?, is the longitude of 

 St. Agnes, west of Greenwich. 



art. xxiv. — Remarks. 



I have shewn, with attention to minuteness, the manner in, 

 which the latitudes and longitudes of the stations on which 

 directions of meridians have been observed are determined. It 

 now remains to be considered, how far the uncertain state 

 in which we remain, with respect to the figure of the earth, may 

 affect the accuracy of those conclusions. 



If the earth were homogeneous, it would necessarily be an 

 ellipsoid; and, were its diameters known, the longitudes and 

 latitudes of places on its surface might be accurately computed, 

 provided their geodetical situations were correctly ascertained, 

 and the latitude of one station in the series of triangles truly 

 determined. 



As there is, however, great reason to suppose that the earth 

 is not any regular geometrical figure, from the impossibility of 

 reconciling the results of the various measurements for ascer- 

 taining the lengths of degrees of latitude, some uncertainty must 

 remain with respect to our deductions ; but there seems to be 

 reasons for supposing the errors, thence resulting, are confined 

 within moderate limits. 



