then tlieland about tkem,and higheft in the middle; the 
chieffprings that caufe them being commonly about the 
middle, from whence they dilate themlelves by degrees,as 
one would blow a bladder; but not always e^jually, be- 
caufe they lometimes meet with greater obftacles/on ohe 
fide, then on the other: whoever has feen Bogs, carinbt'^* 
doubt of this^ and befides if you cut a deep rir^ench thro' 
a Bog ; you will find the originall fpring, 6c vaft quSntitys 
of water will run away, and the i^^?^ lubfide ; the Bog at ^ 
Cafile ForbeSy (as I was informed,) fubfided 30 foot; I 
could hardly believe thatj but found by computation, 
that it could not be much lefs then half of it: I believe, 
thefe, and other obfervations that might be made being 
laid together,it is hardly to be doubted^but that Ihave giv- 
en the true origine ofSo^j-.'thofe hils^that have no fprings, 
have them notjthofe that have fpriags^and want culture, 
conftantly have them: where ever they are, there are 
great fprings : the turf generally difcovers a vegetable 
lubftance: it is light, and impervious to thevi^ater; the 
ground under it is very pervious : and all thefe are 
, plainly ^accountable from the caufesl have given. 
; I ipuli confefs there are quakingBogs, caufed other- 
wife j when a ftream, or fpring runs thro' aflat; if the 
pafFage be not tended,it fills with weeds in Summer, trees 
. fall acrofsit, anddamitup ; then, in winter, the water 
ftagnates farther & farther every year, till the whole flat 
be covered ; then there grows up a courfe kindofgrafs 
peculiar to thefe Bogs ; this grafs grows in tufcs, and 
I their roots confolidate together, and yearly grow 
I higher , in fo much that I have feen of them to the hight 
of a man; the grafs rots in winter, and fals on the 
j tufts, and the feed with it, which fprings up next year, 
and fo ftill makes an addition; fome times the tops of 
flags and grafs are inter-woven on the furface of the wa- 
ter, and this becomes by degrees thicker, till it ly like a 
cover on the water % then herbs take root in it , and by a 
