4 74 * Account of a 
The situations of those stations which are common to this 
operation and that of General Roy, are not described, the 
same being done in the LXXXth Volume of the Philosophical 
Transactions. 
As it is probable that some individual will avail himself of 
the particulars given ill this performance, by forming more 
correct maps of the counties over which the triangles have been 
carried, and who consequently may wish to visit certain of the 
stations, it is proper to observe, that small stakes are placed 
over the stones sunk in the ground, having their tops project- 
ing a little above it. For some years there will be little dif- 
ficulty in finding the stations, as the spots are well known to 
the neighbouring inhabitants. 
SECTION THIRD. 
Measurement of the Base of Verification on Salisbury Plain with 
an Hundred Feet Steel Cham , in the Summer of the Tear 1794. 
art. 1. Apparatus provided for the Measurement , and the Me- 
thod of using particular Articles of it. 
The apparatus with which this base was measured arrived 
at Beacon Hill the 25th of June, and consisted of the two steel 
chains, the tressels belonging to the Royal Society, and the 
twenty coffers which were used on Hounslow Heath, together 
with the pickets, iron-heads, and a few other articles, which in 
the beginning of this year had been made at the Tower. As 
it was foreseen that the truth of this measurement would, in a 
great degree, depend on the accurate reduction of the several 
hypotenuses to the plane of the horizon, an application was 
