[ 498 ]• 
have been informed of two places in particular, extremely 
convenient for the purpofe. The one is lituated on the 
confines of Yorkfliire and Lancafliire ; where, within the 
compafs of twenty miles, are fituated four very remarka- 
ble hills, called Pendle-hill, Pennygant, Ingleborough,, 
and Whernfide, which have been eflimated to be from 
600 to 750 yards elevated above the plane of the vales 
between them. By calculation on thefe data^ it fliould 
follow, that the fumof the contrary attradtionsof Whern- 
lide,. the largeft of thefe hills, on the plumb-line placed 
half-way up the hill, would not be lefsthan 3 o", and might 
amount to 46^', which it is evident is a very confiderable 
quantity, and futhdent to give us room to hope for a far 
vourable and fatisfadory fuccefs ot the experiment. T he 
other place pointed out for this purpofe, is a valley two 
miles broad, between the hills Helwellin and Skidda, in 
Cumberland,; which hills, according to a plan of them and 
the adjacent country, communicated by Mr. smeaton, 
F . R .s .are elevated above 1000 yards above the intermediate 
valley- By a calculation made according to this plan, the 
fum of the contrary attradions of the plumb-line, placed 
alternately on the North- fide of Helwellin and theSoutli- 
lide of Skidda, amounts to about 20", which is likewife 
a quantity large enough for the experiment. And al- 
though the denfity of the earth near the furface fliould 
be five times lefs than the mean denfity, as there is fome 
reafon to fufped, and the attradions, as here flated, fliould 
confequently be diminiflied in the proportion of five to 
one, hill the fum of the contrary attradions of Whern- 
fide 
