Trigonometrical Survey, 555 



art. in. Particulars relating to the Operations of the Tear 1798. 



The object first attained this year, consisted in a trigonome- 

 trical survey of the counties adjacent to the northern and 

 southern shores of the Thames. 



In the last communication it will be seen, that the survey of 

 Kent had been carried on from the sea-coast, till it reached the 

 range which runs eastward from Wrotham through Holling- 

 bourn, and there terminated. The country to the northward 

 could not be surveyed, because the view from General Roy's 

 station at Wrotham is almost entirely cut off, in that direction. 

 In order, therefore, to obtain a base for the purpose, when the 

 party arrived at Wrotham, a new station was chosen, to the 

 eastward of the former one, and the distance between them 

 accurately measured; by which means, together with the included 

 angle at the old station, and the distance of it from Sevemdroog 

 Tower, on Shooter's Hill, a new distance was found, which be- 

 came a base for the survey proposed. 



The chief draftsmen and surveyors belonging to the Drawing- 

 room in the Tower, attended our operations in this county, and 

 also those afterwards carried on in Essex. It was, indeed, for 

 their immediate service, that we renewed the survey in this 

 quarter, as the Master-General had given directions to prepare 

 ample materials for completing the map which meets the public 

 eye with this article. 



The stations in Kent, besides that of Wrotham, were 

 Gravesend, Gad's Hill, and the Isle of Sheppey ; those in Essex 

 were Hadleigh, South End, and Prittlewell. Observations made 

 from these places afforded data for the proposed survey : after 

 they were completed, the small circular instrument supplied the 



