1825.] Diluvial Formations. 37 



convey the waters of the Nene direct to their old channel at 

 Wisbeach, but was never entirely effective before the year 

 1638: when Vermuyden, under King Charles I. erected high 

 banks on each side of the Learn, and opened out a channel to 

 the sea. Since that time the Nene has continued to flow down 

 to the sea by Wisbeach. 



Notwithstanding the indirect nature of the new drainage 

 which conveyed the waters of the Welland, the Nene, and the 

 Ouse, into the sea by the Lynn channel, the fens appear for 

 many years afterwards to have been in a good condition ; a fact 

 which can only be explained by the low level of the great out- 

 fall. In course of time, however, the new channels began to 

 silt up, and new works became necessary. Of these works, 

 the old and new Bedford rivers were the most important, ex- 

 tending from Erith to Salters Lode, a distance of about twenty 

 miles. Soon after the year 1648, when the new Bedford river was 

 completed, the waters of the Ouse were shut out by a sluice at 

 Erith from their old channel, so that they did not mix with the 

 waters of the Cam and its tributary branches, till they had 

 been conducted by the new drainage to Salters Lode. These 

 new works appear from the first to have been injurious to the 

 natural drainage of the Cam; for the floods of the Ouse by the 

 new passage reached Salters Lode much sooner than the floods 

 of the Cam ; moreover, the bottom of the new Bedford river 

 was about eight feet above the bottom of the old Ouse. On 

 both these accounts, the banks of the Cam were perpetually 

 flooded by the back-waters of the Ouse. One great flood of 

 the Ouse in 1720, is said to have backed up the Cam for twenty 

 days, and to have silted up a part of the old channel below 

 Ely, to the thickness of three or four feet. These ruinous effects 

 have been partly counteracted by the erection of different 

 sluices ; which, although affording a cure for an immediate evil, 

 have ultimately produced the very evil they were intended to 

 remedy ; for, partly by their agency, the whole bed of the Cam 

 is now silted up to the level of the Bedford rivers. 



If such extraordinary effects as those described in this note 

 be produced by the accumulation of alluvial matter in course 

 of a few hundred years, we may be well assured that the whole 

 form of the neighbouring coast must have been greatly modified 

 by the same causes acting without interruption, and without any 

 modification from works of art, for 3000 or 4000 years. 



