of an Arc of the Meridian. 411 
I am now to specify, that my intentions were to devote, from 
this period, the whole or the greatest part of the following 
summer, to the use of this sector; nor did I indeed imagine 
such a portion of time more than sufficient. I purposed to erect 
it at Dunnose, and at Clifton, the extremities of my arc ; and 
also at Arbury Hill, near Daventry, the station almost in the 
middle of it. This last station I fixed upon, because it was 
proper to ascertain how far the observations for determining 
the extent of the whole arc, would agree with any others made 
for finding the value of its parts. The erecting of it at Green- 
wich was necessary, for the purpose of observing the zenith 
distances of certain stars, which were afterwards to be observed 
at Dunnose, thereby affording means of ascertaining the lati- 
tude of that station. 
The instrument remained at the Royal Observatory till the 
26th of April ; and, although the weather was for most part of the 
time unfavourable, yet the erecting of it there will be found, as 
appears in a future part of this work, to have answered the pro- 
posed end. One very material service accrued to myself ; this 
was, the advice and instruction I received from the Astronomer 
Royal, for the successful management of the sector, by which I 
scrupulously governed myself throughout the whole of the sub- 
sequent campaign. Having observed the zenith distances of 
some few stars, and made myself completely master of every 
adjustment about the instrument, the sector, with all its appa- 
ratus, was sent to the Isle of Wight, by way of Southampton ; 
every possible care being used to protect it from injury, not only 
while transporting by land, but also when under the act of 
being taken into, and removed out of, the vessel which conveyed 
