459 
Trigonometrical Survey . 
mine the directions of the meridians, the party left London for 
the Isle of Wight early in the month of March, that it might 
arrive at Dunnose in proper time for making the required ob- 
servations. The instrument, however, was first taken to Mot- 
teston Down, for the purpose of intersecting many places 
whose bearings had been last year taken when the instrument 
was at Rook’s Hill, and which were now wanted by the sur- 
veyors of the Ordnance. This station had been selected for 
that purpose, and was never intended to become a principal 
one in the series ; but when the instrument was on the spot, 
it was considered as proper that some observations should be 
made to the stations which were at that time chosen. Jor 
this reason, when the time for observing the star approached, 
and most of the lights had been fired without our having seen 
them, it was not considered of consequence to remain there 
any longer, and the instrument was therefore taken to Dun- 
nose. 
A small staff, of about three inches diameter, was erected 
on Brading Down, which is about six miles from the station, 
for the purpose of referring the star to it ; a small lamp of six 
inches diameter, constructed upon the same plan as the large 
ones, being, when made use of, buckled at the bottom of the 
staff. 
As the best method of obtaining the direction of the meri- 
dian, is by observing the star upon each side of the pole, 
whence the double azimuth is nearly obtained without any 
correction for the star’s apparent motions, every opportunity 
was watched, of observing it at the times of its greatest appa- 
rent eastern and western elongations. But in the unsettled 
season of the month of April, when almost every wind brought 
