XXVI TOPOGRAPHICAL REMAKES. 



the Old River Nene (passing by March) and the cut called 

 Bevill's River on the other ; the two remaining boundaries 

 being the adjoining counties of Norfolk and Huntingdon. 



No. 8, Wisbech, includes all that part of the county 

 which lies to the north of No. 7. This is the most 

 continuously fenny tract included in our Flora : its fen- 

 islands are small and few in number : but, as has been 

 already stated, the silted-up estuary of the Ouse forms a 

 remarkable feature at its northern extremity. 



If now we reconsider these districts we may combine 

 them so as to divide the county into three unequal parts, 

 which may be called the Chalk, Clay, and Fen Tracts. 



A, Chalk, is a tract formed of the districts 1 and 2, 

 in which nearly all our chalky land is included. B, Clay, 

 includes 3, 4, and 5 which, if the border of the Fens is 

 excepted, lie almost wholly on the Boulder Clay, Gault, or 

 Kimmeredge Clay. C, Fen, consists of the remaining 

 three districts 6, 7, and 8. 



The Map in outline will illustrate these Districts, but 

 they can only be traced exactly upon the Ordnance 

 Map : nevertheless this small sketch will probably suffice 

 in most cases. 



The county of Cambridge is about 50 miles in length 

 from north to south, and its greatest breadth is 25 miles. 

 It is said to contain nearly 550,000 acres. It lies wholly 

 between the 52 and 53 parallels of Latitude, and the town 

 of Cambridge is situate 5 miles to the east of the meridian 

 of Greenwich. We learn from the observations of the 

 Rev. L. Jenyns that the mean temperature of the seasons 

 is, Spring 47.18°, Summer 60.87°, Autumn 49.86°, and 

 "Winter 38.09°. The mean annual range of the Barometer 

 is 1.890 inches. The mean fall of rain about 22.5 inches. 



