[ S°7 ] 
the zenith being equal to the latitude of the place. The 
contrary happens on the North lideof the hill; the lower 
extremity of the plumb-line being there carried South- 
ward will occafion the apparent zenith to be carried 
Northward or from the equator; and the latitude of the 
place will appear too great by the quantity of the attrac- 
tion. Thus the lelTer latitude appearing too fmall by the 
attraction on the South fide, and the greater latitude ap- 
pearing too great by the attradfion on the North fide, 
the difference of the latitudes wall appear too great by 
the fum of the two contrary attradlions; if therefore 
there is an attradlion of the hill, the difference of latitude 
by the celeftial obfervations ought to comie out greater 
than what anfwers to the diflaiice of the two fcations 
meafured trigonometrically according to the length of a 
degree of latitude in that parallel, and the obferved dif- 
ference of latitude fubtradled from the difference of la- 
titude inferred from the terrelfrial operations, will give 
the fum of the two contrary attradfions of the hill. To' 
afcertain the diflance between the parallels of latitude 
palling through the two llations on contrary lides of the 
hill, a bafe miifc be meafured in fome level fpot near the 
hill, and connedted with the two hatioiis by a chain of 
triangles, the diredlion of wdiofe lides, with refpedi; to the 
meridian, llrould be fettled by alironomical obfervations. 
If it be required, as it ought to be, not only to know 
the attraddon of the hill, but alfo from thence the pro- 
portion of the denfity of the matter of the hill to the 
mean denlity of the earth ; then a. furvey mult be m.ade 
of 
