84 On the Origin and Distribution of the British Flora.
Cambridgeshire border, and flows eastward to Wixoe, where
it begins to form the boundary between Suffolk and Essex.
Its drainage-area is variously stated at 430 or 407 square
miles, most of which is in Suffolk, and its length as 45 or 55
miles : probably the smaller number is the true one in each
case. Its chief tributaries are the Suffolk rivers, Brett,
Boxford, and Orwell, but from Essex it receives four small
streams: one above Sudbury, from Ovingten, Wickham
St. Paul, and Belchamp Water; another below Bures, from
Pebmarsh; a third at Neyland, from West Wood Green;
and, below Langham, one from Boxted Heath.
In the seventh and last sub-province, the Brook rises
between Debden and Ugley, and flows northward, receiving
the water from Debden Lake, through Quendon, Newport
(where it receives a stream from Arkesdon), Wendon (where
it receives another, also on its left bank, from Chishall and
Wendon Lofts), and Audley End, where it receives the
Slade, to Chesterford, where it leaves the county. The Slade
rises between Hadstock and Little Chesterford, and flows
under the town of Saffron Walden. The Brook is a tributary
of the Cam or Granta, and is spoken of by both these names.
Probably Granta is merely a scholastic form of the name
Cam, as Isis has been coined at the sister University. The
main stream of the Cam rising in North Hertfordshire is
sometimes termed the Rhee. The question as to which of
these sources and streams is the main river is, like that
between the Churn and the Thames Head Brook, one of no
real importance or possible solution. Such being the prin-
cipal watercourses of the county, my sub-provinces depend
upon their watersheds, as follows :—
Sub-province 1—Lea and Stort. From 7, by line from
Little Chishall to Langley, Rickling, Ugley, and Henham-
on-the-Hill ; from 2 and 4, by this line continued to Broxted,
Little Canfield, White Roding, High Laver, North Weald,
Epping, High Beach, Walthamstow, Wanstead, East Ham,
and North Woolwich.
Sub-province 2—Roding and Small Thames affluents. From 4,
by line from Broxted, through Easton Park to High Easter,