54 2 The Account of a 



Before I close this Introduction, I am to announce, that Mr. 

 Isaac Dalby, no longer able to endure the fatigues incident to 

 the service, has retired from it ; and it would be a matter of 

 injustice, if I were not to acknowledge the extent of his services, 

 his unremitted labour, and attention. But, whilst I lament the 

 loss of a man so perfectly calculated to assist me in this arduous 

 undertaking, I derive every consolation from a knowledge, found- 

 ed on experience, of the talents and abilities of Mr. Simon Wool- 

 cot, his successor. 



SECTION FIRST. 



i. Particulars relating to the Operations of the Tear 1797. 



The principal object proposed to be accomplished this year, 

 was the determination of the directions of meridians at proper 

 stations, in order to afford the necessary data for computing the 

 latitudes and longitudes of places intersected in the surveys of 

 1795 and 1796. 



From errors which are the result of computations made on 

 the supposition of the earth's surface being a plane, it is expe- 

 dient that new directions of meridians should be observed, when 

 the operations are extended, in eastern or western directions, over 

 spaces of sixty miles from fixed meridians. The distance from 

 Dover to the Land's End being upwards of 300 miles, it becomes 

 necessary, on this principle, that four directions of meridians 

 should be observed ; which, with that of Greenwich, amounts to 

 five, dividing this space into six nearly equal parts. 



Whatever be the stations farther to the westward, which offer 



