76 
Mr. Aikin on the V allies and Watercourses 
namely from Newtown to tideway at Gloucester, a distance of be- 
tween 160 and 140 miles, not only the entire fall, but the descent 
through particular portions of this space are very correctly ascer- 
tained ; and, there being neither weir nor lock nor any other arti- 
ficial obstruction to the free course of the stream from the source of 
the river to its mouth, the ambiguity arising in other cases from 
these causes has no place in the present inquiry. 
The Severn continues to be a torrent incapable of navigation to 
Pool-Quay, about twenty miles below Newtown, in which space 
it descends 220 feet, being at the rate of 1 1 feet per mile. From, 
Pool-Quay to Bagley brook at Shrewsbury, a distance of twenty- 
six miles, the entire fall is 96 feet, being at the rate of 3 feet 8 inches 
per mile. The descent however through this space is by no means 
equable; for the river, which while in its own valley has banks only a 
few feet in height, no sooner gets into the alluvial plain of Shrews- 
bury than it has the appearance of a ditch bounded by steep banks 
of gravel from 12 to 20 feet deep, the banks themselves at the same 
time not being sensibly higher than the rest of the marshy district 
which is thus intersected. Formerly, when these marshes had not 
been embanked, the greater part of the flood waters extended them- 
selves over this open space, and returning slowly into the bed of 
the river kept up for many days a depth of water amply sufficient 
for the purposes of navigation. At present however, now that all 
these low lands are secured by substantial embankments, a heavy 
fall of rain of thirty-six hours duration swells this part of the river 
into a turbulent torrent, rising from 10 to 20 feet perpendicular in 
as many hours, and declining almost as quickly from its greatest 
height to its usual shallowness. 
From Bagley brook at Shrewsbury to Coalport (about two 
miles below Coalbrook-dale), the entire distance is about twenty-one 
