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XX. An Account of the Trigonometrical Survey, carried on in the 

 Tears 1797, 1798, and 1799, by Order o/"JVTarquis Cornwallis, 

 Master-General of the Ordnance. By Captain William Mudge, 

 of the Royal Artillery, F. R. S. Communicated by his Grace 

 the Duke of Richmond, F. R. S. 



Read July 3, 1800. 



INTRODUCTION. 



Having interspersed in the following Paper, with as much 

 attention to brevity as the subject admits, every intelligence 

 relating to the Trigonometrical Survey, I think it unnecessary 

 to swell the bulk of the communication, by giving a long pre- 

 fatory account of its progress since the year 1 J96. 



The contents of the work now meeting the public eye, are 

 important and numerous : I have divided it into sections. The 

 first contains the calculations of the sides of the principal and 

 secondary triangles extended over the country in 1797, 1798, 

 and 1799 ; together with an account of the measurement of a 

 new base line on Sedgemoor, and a short historical narrative of 

 each year's operation. The second section contains the computed 

 latitudes and longitudes of those places, on the western coast, 

 intersected in 1795 and 1796, and also such others, since de- 

 termined, as lie conveniently situated to the newly-observed 

 meridians. This section also contains the directions of those 

 meridians ; one on Black Down, in Dorsetshire; another on But- 

 terton Hill, in Devonshire ; and another on St. Agnes Beacon, 



