132 Some Additional Notes on Essex Watersheds.
the Pym, and the Mardyke. With the exception of a small
area in the north-west, drained by the Cam into the Wash,
the remainder of the 1648 square miles of Essex is drained
by streams running eastward, of which the Crouch, the
Blackwater, the Colne, and the Stour are the chief. Of these
the Blackwater drains the largest area, the portion of the
valley of the Stour in Essex being but a narrow strip of
country. Though there is no doubt that in prehistoric times
these eastern streams, like the Thames itself, formed tribu-
taries of the Rhine, which then flowed down the centre
of the German Ocean, a study of the sand-banks of our
south-east coast shows the Crouch to belong rather to the
Blackwater system than to the Thames.
The watersheds of river valleys form the most obvious
natural division of any area, and as such are now commonly
adopted by naturalists in subdividing a county for the study
of the distribution of plants and animals. For convenience
of reference I have (' Transactions of the Essex Field Club,'
vol. ii., p. 80) numbered the river basins of Essex as
follows :—1, the Lea and Stort; 2, the Roding; 3, the
Crouch ; 4, the Blackwater: 5, the Colne : 6, the Stour;
7, the Cam ; and the object of the following notes is to give
some additional particulars and corrections which have sug-
gested themselves since my former paper was printed.
The source of the Lea is in Leagrave Marsh, near Dun-
stable ; and this river drains two-thirds of Hertfordshire.
Among its tributaries, the Nasing Brook, entering below
Broxbourne, and the Ching, above Walthamstow, from the
Forest, were not previously mentioned. Its watershed is
south of the church at Henham-on-the-Hill; a line from here
to the west of Chickney and Broxted, east of Elsenham and
west of East-end Wood, divides the Stort valley from that of
the Chelmer; and the former is then separated from that of
the Roding by a line passing between Colchester Hall and
Lever's Farm to Warish Hall and Takeley Railway-station,
east of Barrington Hall and Hatfield Broad Oak, west
of Manning Farm and White Roding, to the south-east
of Little Laver, between Househam Tye and Holt's Green to