TRANSACTIONS OF THE SECTIONS. 47 
of the old channel at Salter’s Lode; and the floods from the upper parts of the Ouse 
commonly reached this spot, through the straight artificial channels, much sooner 
than the floods of the Cam. A new and unlooked-for evil was the consequence; the 
banks of the Cam were continually liable to floods from the back-waters of the Ouse. 
One great flood of the Ouse, in 1720, is said to have backed up the Cam from Sal- 
ter’s Lode, for twenty days, and to have silted up one part of the old channel below 
Ely to the thickness of three or four feet. Ruinous effects of this kind were pre- 
vented by the erection of various sluices, of which Denver sluice was most effective. 
But although affording a cure for an immediate evil, and necessary to the internal 
navigation of the Great Level, they have ultimately contributed to the very evil they 
were intended to remedy ; for partly by their agency the whole bed of the Cam (as 
well as of the old Ouse below Ely) was gradually silted up to a much higher level, 
injurious to all the neighbouring fen-lands. The causes which produced these re- 
markable changes continued to operate, and from time to time compelled the execu- 
tion of new works. By way of conclusion, those works which have been effected 
within the last thirty or forty years may be briefly noticed :-— 
1. All the fen-lands, in the interior of every part of the great Bedford Level, are 
so far above the mean level of the sea, that they might be effectually drained by 
artificial cuts to low-water mark ; and the drainage might then be maintained per- 
manently and effectually without the enormous expense of water-mills and other 
artificial means. This has been partially effected by great works near the mouth of 
the Witham, and by other similar works to the north of Morton’s Leam, which 
give a natural and uniform descent to the waters of Thorney fen and a part of South- 
Holland fen. 
2. Within the same period a new channel has been cut for the Nene below Wis- 
beach, and by an artificial embankment the upper part of the estuary has been gained 
from the sea. Since then the lower part of the estuary has continued to warp up to 
a higher level, and other artificial encroachments upon the sea are now in progress. 
Had the bed of the Nene been lowered as far as Guyhirn, many thousand acres of 
unreclaimed fen (including Whittlesea-meer) might have been drained by a direct cut 
to that place. At present there is a violent rapid which conveys the waters of the 
upper level to the level of the new river course below Wisbeach. In consequence 
of this most injurious condition of the Nene, works are now in progress for the 
drainage of Whittlesea-meer and the neighbouring fens by a longer and more indi- 
rect cut to the lower part of the Ouse near Lynn. 
3. A great delta had been formed above Lynn during the time that the waters of 
the Bedford Level were discharged (as above described) by the mouth of what was 
once called the Little Ouse. This delta gave a slow discharge to the great land- 
floods and caused much back-water. The artificial cut, called the Eau Brink, has ina 
great measure abated this evil. Many large tracts of fen-lands (on the Cam and the 
Ouse), which were once poisoned by stagnant water, are now well-drained and made 
productive by a top-dressing of clay; and floods, which formerly hung on these 
lands for many weeks, now disappear in a few days. 
Local improvements, from the lowering of the river courses and the introduction 
of steam-power, are not here noticed. Many of them are but local expedients to 
meet an existing evil, which could not recur were a more uniform and systematic 
drainage of the Great Level ever carried into effect. Enough has been stated in this 
Appendix to explain the appearance of forest-trees and other indications of dry land 
in many places of the Great Level, now sunk under many feet of bog-earth and allu- 
vial silt: aud if such remarkable effects have been thus produced by the accumula- 
tions of alluvial matter and the growth of fen-land in the course of six or seven hun- 
dred years, we may be well assured that the whole form of the neighbouring coast 
must have been greatly changed in more ancient times by the same causes acting 
without interruption and with less modification from the works of man. 
On the occurrence of Silurian rocks at the villages of Ober and Neu Schmollen, 
near Breslau, in Silesia, and covering an area of about eight square English 
miles. By M.Ferpinanp Oswatp of Oels, in a letter to Mr. Murcuison, 
Mr. Murchisun considered this an interesting discovery, as throughout Germany 
