lelf into the hoie, and the noife dotky in alllikelyhood^^ 
proceed from a fubterraaeousftream; which in Summer 
has Foom enough to vent all its watersbut in winter, when 
rains fall, the paffages between the Rocks cannot vent 
the water, and therefore it regurgitates, and covers the 
flats. 
Let G be a plain par^Lllell to the horizon ; let AAA 
beahiib 5iVS a flat; CCC another h^l ; D iS^O ano- 
ther flat; and EJEE another hill ; let i. /M be a lub- 
terraneous rivulet, that runs under the furface of the 
Earth ; at M let there be a narrow paffage, which can 
only Vent fuch a quantity of water ; the head of the river 
above L is fuppofe higher then the flat B NB or DNDsthe 
current fuppofe is fwoln with rain, and brings more wa- 
ter to A/, then can pafs : it is plain the refl: muft fill the 
paflage L I and at k fl: burft out at iViVjthe holes fuppofd 
in the flats, and cover the flats ; and by this means the 
wholeCountry in the winter feems full of Lakes,- and a- 
gain in Summer,when the paflage Mis big enough for the 
water of the rivulet, the water (ubfides and falls thro' the 
holes iVNinto the fubterranean pafl^ages and in a littie 
time leaves the flats dry till the next year. 
Thefe Turloughs are hard to drain ; often they are en- 
circled with hils, and then 'tis not to be expedled : often 
they have a vent by which they fend out a confiderable 
ftream; and then it is only making that paflage as low, as 
the bottom of the flat, and that will prevent the over- 
V flowing 
