786 Mr. hutton’s Calculations to afcertain 
as many more points as poffible in the furvey may be 
feen from it. A ffume as many principal or eminent 
points and objects as may be proper and convenient ; and 
from each one of them meafure the angles formed by 
all the reft that can be feen, both horizontal and vertical 
angles, and repeat thefe obfervations, if convenient, with 
the inftrument varied or reverfed, taking the means 
among the feveral quantities of each angle. Take then 
as many feCtions of the ground, and as far extended in 
all directions, as the time and circumftances will pofiibly 
admit. Of the feCtions, thofe that are horizontal or level 
are the belt, as they require no calculation ; procure 
therefore as many as poffible of them. In vertical fec- 
tions obferve the vertical angles, not in the plane of the 
feCtion, but at fome other point of which the bearing is 
alfo taken from the beginning of the feCtion line, and 
where the horizontal angles of the poles are taken, for 
the reafons before mentioned in p. 723. And it will be a 
ftill farther convenience if the fedtion be made in fuch 
direction as to form a right angle with the line drawn to 
the point or ftation from whence the vertical angles of 
the poles are obferved, as may be feen from what is faid 
in p. 7 2 1 . It might, perhaps, be proper to make fome 
experiments on a valley inftead of a hill, taking two ob- 
fervatories at the two oppofite tides of it, both for the 
greater 
