674 The Account of a 



The Observatory of his Grace the Duke of Marlborough, at 



Blenheim. 



The staff erected over the quadrant, was observed from 

 White Horse Hill and Whiteham Hill. At the former station, 

 the latter makes an angle of 36° 30' 13",5, with the parallel to 

 the meridian of Dunnose. The staff, therefore, bears from the 

 parallel 25 59' 29", 7 5 N E. ; consequently, its distance from the 

 meridian of Dunnose is 36540 feet, and from the perpendicular 

 446458 feet. These respectivelysubtend5 / 58'',3,andi°i3 / 2i / ',4; 

 therefore, the latitude of the Observatory is 51 50' 28",3, and its 

 longitude 9' sg",Q fr° m Dunnose : but i° n' 36" is the longitude 

 of that station ; therefore, i° 21' 15",9, or 5' 25",2 in time, is the 

 longitude of the Observatory west from Greenwich. 



As the meridian of Dunnose passes at no great distance from 

 that of Blenheim, I have deduced the latitude and longitude from 

 the former, to avoid the errors which creep in, when computa- 

 tions are carried on from remote meridians. It may be worth 

 while, however, to show that the extent of those errors would 

 not be great, were the meridian of Dunnose neglected, and 

 the Observatory at Blenheim referred to the meridian of 

 Greenwich. 



The distance of White Horse Hill from the meridian of Green- 

 wich is found to be 356050 feet, and from its perpendicular 

 39425 feet ; the bearing of Nuffield, from the parallel at that 

 station, being 89° $g' 27" S E. Blenheim will, therefore, be found 

 to bear 26°55' 25" N E from the parallel at White Horse Hill; 

 consequently, its distance from the meridian of Greenwich is 

 307224 feet, and from its perpendicular 13556^ feet. These 

 give the arcs 50' 12",4, and 22' i6",i ; from whence we get 

 51 50' 28",! for the latitude, and 1 8 21' 16" for the longitude, 



