it i eel ee 
- Jn Ba ae ee . 
ACGOUNT of PEAT-MOSSES, &c. 267 
ed in the extent above mentioned, except that the Dript rock is 
continued acrofs the river, and that another rock alfo crofles it, 
at what are called the cruives of Craigforth, and gives a confi 
derable obftrudtion to the ftream, fo as to prevent the tide from 
flowing up farther. Throughout the reft of the carfe, no 
ftones whatever are found in the foil; but beds of fea-fhells, 
particularly oyfter-fhells, appear in many places of it, as in 
ditches, where the earth has been dug to a certain depth, 
and in the banks of the Forth and its branches. A bed 
of this kind, of confiderable thicknefs, is to be feen near- 
the bridge of Goody, a fmall river that runs into the Forth ; 
and another is to be feen in a bank, on the fouth fide of the 
road between Polmouth and Borrowftounnefs. When the Forth 
encroaches upon its banks, it alfo difcovers large logs of tim- 
ber at various depths in the clay. 
CoNncERNING the river it may be neceflary to remark, that 
the tide flows as far as the bed of rock near Craigforth, al- 
ready mentioned, which is about 300 yards below the junc- 
tion of the Teith and Forth: Above this point, the furface of 
the river is four feet and a half higher than the furface below, 
even at {pring tides. The only other fall in the river from that 
place to Cardrofs, where the carfe terminates, is one of three 
feet at the ford of Frew, about eight miles diftant from the 
former, in a ftraight line. 
Ir will ferve to give fome idea of the flatnefs of this country 
to obferve, that by a furvey taken of the river, with a view to ren- 
der it navigable, it was found, that a dam four feet in height, 
erected at the point of Craigforth, would increafe the depth of the- 
river more than three feet as far up as the ford of Frew; and 
that one of five feet in height, erected: at Frew, would make a 
like addition to the depth of the river, as far as the ford’ of Car- 
drofs. The height therefore of the furface of the Forth, at the 
ford of Cardrofs, above the high water mark at the cruives of 
Hil} 2 Craigforth, 
