418 An Account of the Measurement 
that the sector was not set up over the old station, as injury to 
some amount would have been sustained by the person farming 
the soil, owing to its cultivated state. The spot on which I 
fixed, was 34 feet to the north, and 28 towards the west, of the 
former station. 
Of the stars seen at Clifton, 12 were observed at Arbury 
Hill. These observations were continued, with very little inter- 
ruption, till the 4th of October, when the party, with all the 
apparatus, returned to London ; the zenith sector being found 
as perfect on its return as when first sent into the field, a cir- 
cumstance inferring both the strength and perfect union of its 
parts. 
Particulars relating to the Measurement of a new Base Line , on 
Misterton Carr , in the Tear 1801. 
The apparatus used for the measurement of this base, was 
the same as that employed on Hounslow Heath, Salisbury Plain, 
and Sedgemoor; and the like pains were taken to ensure its 
accuracy, as were used on those occasions. The points for lining 
out the base were put into the ground with great truth and pre- 
cision ; the large theodolite being used as one of the means, and 
in the same way as in measuring the base on Salisbury plain. 
Previous to the commencement of this operation, two large 
blocks of oak, with square holes on their upper surfaces, were 
sunk in the ground, at the extremities of the base ; the point of 
intersection of the diagonals of each hole, severally denoting 
them. These diagonals were drawn on lead, cast into the holes, 
and ground to a smooth plane, even with the surface of the 
block. 
Before the measurement began, the working chain A, and the 
