44$ The Account of a 
more than once : indeed it was a position which we laid down 
upon our commencing this business, and which, as far as cir- 
cumstances would admit, has since been adhered to, namely, that 
of observing the angles upon different arcs. When staffs vvere 
erected, which was generally the case when the stations were 
not more remote than fifteen miles, the angles were repeated 
till their truth became certain, and the same was also done, 
when angles were determined by the lamps ; but it sometimes 
happened, that only one of the two white lights, which were 
burned at the distant stations, was seen ; in which case, if the 
observation appeared to be made without any error, but that 
which an inequality in the division of the instrument might 
be supposed to produce, it was considered as sufficient ; other- 
wise fresh lights were sent to the station and observed. 
In the use of the white lights, it is conceived that sufficient 
precautions were taken, as the firing of them was always com- 
mitted to particular soldiers of the party, selected from the rest 
on account of their capacity and steadiness, who had instruc- 
tions to place the copper nozle immediately over the point 
marking the station, by means of a plumb-line let fall from the 
bottom. In observing them with the instrument, the angle 
was not taken till the light was going out. But the men com- 
monly guarded against the flame being blown greatly on one 
side, by erecting something to windward of the light. 
In the use of the lamps also, care was taken to give them 
their proper direction ; for when the ground about the station 
would not admit of the lamp being placed immediately upon 
it, slender staffs were erected supported by braces, and made 
upright, by being plumbed in directions at right angles to each 
other. Precautions were also used to put those staffs pre- 
