264 
THE MIDDLE LIAS OF NORTHAMPTONSHIRE. 
the Nen valley, such flood will follow within 24 hours, and 
generally in less time than this. It is not uncommon for a 
flood to be at its highest in 12 hours. In winter J inch of 
rain in 24 hours is sufficient to cause a flood, in summer time 
from 1 to 1J inches in the same time, depending upon the 
previous condition of the land. Floods in winter time will 
often last for weeks together in the Nen valley, and the 
ground most subject to these floods be unfit for stock for quite 
half the year. They are regarded as half-yearly lands. 
2. —Agricultural Drainage.— Although I have placed this 
second as an individual cause of floods, it must be regarded 
as quite subordinate to the one just considered, inasmuch as 
drainage is only intended to get rid of excess of water which, 
in most cases, has only a short time previously fallen as rain. 
I also wish it to be understood that I do not consider it equal 
to the aggregate of the other natural and artificial causes to 
be enumerated. 
The advantages of land drainage in a country like England 
are so obvious that few words are required on this matter. It 
is very probable that, because of the considerable and evident 
benefits often derived from drainage, as with other good 
things, it has, in some cases, been imitative and indiscrim¬ 
inate, and therefore excessive. 
There is no doubt it is much better for rain water to pass 
through the soil than simply over its surface, within certain 
limits as to quantity. In the latter case it will take much 
away, but not add anything itself, whereas in the former it 
will generally enrich rather than impoverish the land, so far 
as useful plant food is concerned. The rapid removal of 
water from the surface of ground is very desirable, both for 
the good of human beings and animals breathing the atmos¬ 
phere above it, and for plants being grown in it. The tem¬ 
perature of well drained land is higher, and plant growth in 
consequence more rapid, and cultivation generally is a much 
easier and less precarious operation.. 
I know the opinion is held by some, that drainage has not 
been and cannot be carried to excess. It is asserted that 
undrained lands may suffer most in dry weather, for stagnant 
water in the early part of the year retards vegetation very 
much, and renders it more liable to damage from late frosts, 
both of which causes tend to produce a scanty herbage, or 
less luxuriant crop on arable land, and if the weather is hot 
and dry in May and June, they will both suffer more than if 
the crop had been more luxuriant and the ground better 
covered; that is, the productive capabilities of the soil are 
reduced to a minimum. If we accept this explanation, and 
