[ 71 ] 
he pleafes, with a fufficient degree of accuracy, if, 
with this inftrument, he takes the angles fabtended- 
by two or three pairs of objedls properly chofen uporii 
the (hores round about him ; but it will be ftill bet- 
ter to have two obfervers, one of whom, being in a 
boat, muft, at the time he takes the angle fubtended 
by fome two objedls upon the ihore, make a fignal to 
the other obferver, who, being placed at one of the 
objedls, as a flation, muft at the fame time obfervethe 
angle fubtended by the boat and the other objedt. 
By this means, two angles in a plain triangle being 
given, together with the diftance between the two> 
objedts, as a bafe, the whole triangle, and the fitu- 
ation of every part of it, will be given likewife. 
By fuch obfervations, as thefe, provided the boat be 
at red: during the time of making them, and they 
be made carefully, with good quadrants, though 
without the afiidance of telefcopic fights, the fitua- 
rion of places may be eafily determined to twenty or 
thirty feet upon every three or four miles. 
Befides the ufe of Hadley’s quadrant in furveying, 
it may upon fome occafions be very ad vantage on fly 
employed in piloting fliips into harbours, the great 
readincfs, with which it may be ufed, making it a 
very convenient inftrument for this purpofe : but that 
this may be done to the greatefl advantage, it will 
be necefiary to have a proper provifion made for it 
upon the charts, by exprefiing upon them the angles 
fubtended by given objedts, by means of which, to- 
gether with the bearings, a flilp may be enabled to 
know her fituation with areat exadlnefs. The well- 
O 
known property of the circle, that angles in the 
fame fegment are equal to each other, may be often- 
times 
