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 Boding; 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 Cliing, above Walthamstow, from the 
Forest, were not previously mentioned. Its watershed is 
south of the church at Henham-on-tlie-Hill; a line from here 
to the west of Cliiclmey 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 Boding by a line passing between Colchester Hall and 
Lever’s Farm to Warisli Hall and Takeley Railway-station, 
east of Barrington Hall and Hatfield Broad Oak, west 
of Manning Farm and White Boding, to the south-east 
of Little Laver, between Househam Tye and Holt’s Green to 
