14 Doctor hutton’s Determination , &c. 
•2929 a. Which fhews that the other limit is ^ ; that 
is, when the hill is extremely low, the point of great- 
eft attraction is at ^ of the altitude, like as it is at 
when the hill is- very fteep. And between thefe limits it 
is always found, it being nearer to the one or the other 
of them, as the hill is flatter or fteeper. 
27. Thus then we find that at i of the altitude, or 
very little more, is the beft place for obfervation, to have 
the greateft attraction from a hill in the form of a tri- 
angular prifm of an indefinite length. But when its 
length is limited, the point of greateft attraction will 
defcend a little lower ; and the fhorter the hill is, the 
lower will that point defcend. For the fame reafon, all 
pyramidal hills have their place of greateft attraction a 
little below that above determined. But if the hill have 
a confiderable fpace flat at the top, after the manner of 
a fruftum, then the faid point will be a little higher 
than as above found. Commonly, however, \ of the 
altitude may be ufed for the beft place of obfervation, as 
the point of greateft attraction will feldom differ fenfibly 
from that place. And when uncommon circumftances 
may produce a difference too great to be intirely neglect- 
•r 
ed, the obferver rauft exercife his judgment in guefftng 
at the neceffary change he ought to make in the place 
of obfervation, fo as to obtain the beft effect which the 
concomitant circumftances will admit of. 
