Trigonometrical Survey. 567 



in hand. When the observations were made on Severndroog 

 Tower, in the year 1787, the angle between Hanger Hill Tower 

 and the cross on the dome of St. Paul's was taken : this was now 

 made use of, in order to get the angle between Hanger Hill 

 Tower and Hampstead Heath ; because the former station could 

 not be discovered, on account of the wind blowing the thick and 

 darkened atmosphere of London between the stations, when the 

 instrument this year was carried to Shooter's Hill. 



For the purpose of connecting the eastern and western tri- 

 angles with each other, a station was chosen on Southweald 

 Tower, accessible only to the small instrument. Brentwood 

 Spire was also found to be conveniently situated for carrying on 

 the distances : this will be readily perceived by the plan. Lang- 

 don Hill was also selected ; which, with the former station at 

 Gravesend, were to become the means of connecting the tri- 

 angles. A station on Epping Forest was judged necessary ; 

 but no spot could be found lit for general purposes, the view 

 towards the north being confined. One was, however, fixed on, 

 called Highbeech, from which a high building near Berkham- 

 stead was found to be visible, by means of which, the distances 

 in the north of Essex could be verified, as the station on the 

 top of it would connect with Bushy Heath, near Watford, and a 

 point on the elevated range near Dunstable. 



From Hampstead, the instrument and portable scaffold were 

 carried to Langdon Hill, and from thence to Triptree Heath, 

 near Maiden ; from whence the party repaired to Highbeech, 

 leaving the remainder of the county to be surveyed with the 

 small circular instrument ; which seems to have been done with 

 considerable accuracy. 



After the necessary observations were made at Highbeech, I 



4D2 



