52 
Trunk Drainage. 
who live within the ranpe of their influence ; that influence is 
not confined merely to the low grounds on the margin of the 
river. The malaria, or noxious exhalations, rise by their light- 
ness and impinge against the neighbouring heights, thus affecting 
the health of places high above the level of the river These 
miasmata attach themselves to the hydrogen gas, usually evolved 
in situations where there is stagnant water or decaying vegetable 
remains. With the hydrogen they rise into the atmosphere, and 
the aerial poison is thus often carried far and wide from its 
primary source Beside fevers of a severe and even malignant 
kind, the exhalations in question are calculated to produce 
chronic disorders of the digestive organs, and those tedious liver 
complaints which are so prevalent in this county ; more especi- 
ally in those localities near to rivers and large brooks The 
prevalent diseases of our district are such as have cold and damp 
for their remote and predisposing causes. I need only enumerate 
scrofula (in its various modifications of pulmonary and glandular 
disease), disorders of the alimentary canal and of the liver, and 
also rheumatism, acute and chronic, with the premature infirmity 
so often entailed by it, as tlie more common diseases of this 
central county, aggravated certainly, if not altogether caused, by 
the cold and damp above referred to." The Nene Valley consti- 
tutes a great laboratory of miasmata ; but a surprising increase of 
salubrity may be certainly looked for as the result of a good 
drainage : as we find in the case of the Fens, more particularly 
the Isle of Ely, a diminution of mortality in thirty years, 1796 to 
1825, from 1 in 31 to 1 in 47, which is about the mean of the 
whole kingdom. Tiie Ouse has a like deadly character, as shown 
by the excessive mortality of Buckinghamshire, Huntingdonshire, 
<Scc. ; and, indeed, so have all our sluggish rivers : exemplified at 
Norwich, surrounded by the heavily-flowing Wensum and Yare ; 
at Colchester, by the dull and tardy Colne ; at Salisbury and 
Bath, by the inactive and cheerless Avon — rivers gloomy and 
lifeless as the Nene. Vet the Avon, at Bath, would naturally run 
off quickly were not its waters held up by weirs, which keep it 
in a perpetual state of stagnancy ; and thus, in the warmer months 
of the year, the air becomes impregnated with the most noxious 
vapours, the death-bringing eflluvia to hundreds who court that 
retreat of fashion. 
Such being some of the inconveniences and calamities of the 
Nene Valley while subject to overflow, what are the obstructions 
which prevent the river with its fine fall of 3i feet per mile from 
carrying off the upland waters pouring into it ? 
Tlie river below Peterhorough has now to carry an extremely 
variable quantity of water, and, as regularity of current in quan- 
tity and velocity is necessary to keep a river or tidal channel 
