TOPOGRAPHICAL REMARKS. XX111 



as it is properly called from Grantchester to Harrimere 1 ) is 

 only known as the Bourn Brook. It passes through a clay- 

 country, and usually conveys a small volume of water, al- 

 though it is sometimes much swollen by floods. 



Districts. — How very difficult it is to divide this county 

 into districts, otherwise than artificially, will be seen from the 

 above remarks. The river-basins cannot be used, for we can 

 hardly be said to have more than one. Indeed it is rather the 

 elevations that point out a difference in the vegetation than 

 the depressions. The fens also are so iiniform in character 

 throughout their whole extent that, but for that extent, they 

 might well be considered as a single district. An endeavour 

 has been made to give as natural a character as possible to 

 the districts : to keep the chalk country separate from the 

 gault : and that from, the fen. To do this artificial bounda- 

 ries are unavoidable ; for it is requisite that they should be 

 lines easily to be traced upon the map, and recognized in the 

 country. Turnpike-roads and main water-courses are there- 

 fore used as boundaries. The county is thus divided into 

 eight districts, of which Nos. 1 and 2 include the main mass 

 of Chalk. No. 3 contains most of the Drift Clay, together 

 with the small tract of Lower Green Sand at Gamlingay: 

 4 and 5 occupy the country bordering on the fen (most of 

 which was formerly very swampy) and a small portion of the 

 fen itself. For fen and " high land," as it is locally called, 

 are so intermixed at their edges that no satisfactory line can 

 be drawn to separate them. The small patch of Suffolk 

 sand at Chippenham is included in No. 5. The remaining 



1 This name is now nearly obsolete. It was a morass or lake 

 formed by the junction of the old channel of the Ouse with the Cam, 

 at about five miles above the city of Ely. 



