On Draining. 
413 
that the worms boro quite as deep as the main (hains, and some 
of the bores are half an inch in diameter ; these, combined with 
the fissures, admit the water to the depth they are formed ; and 
if the fissures and worm-bores, after a continuance of dry weather, 
extend below the level of the minor drains, at the commencement 
of heavy rains the water does not run off, until the fissures and 
worm-borcs arc filled to such a height that there is a fall from 
these side-drains into the main drain itself. I have repeatedly had 
drains cut and allowed to remain open for several days, and have 
always noticed (where there were no springs or sand-veins) that 
although a small quantity of water enters the drain at the sides 
when first cut, this operation of the drain soon ceases, and the 
whole of the water enters on a level with the bottom, which is in 
accordance with the principles of hydrostatics. The water first 
descends perpendicularly by the fissures, worm-bores, &c., until 
they are filled above the level of the conduit of the drain, then 
takes a horizontal direction {by pcrcolatintj sidcioaija throiif/li the 
perpendicular fissures) * to the conduit of the drain, which it enters 
at the bottom ;"t' and no clay land can be thoroughly drained where 
this is not the case, for if the water does not enter into every part 
of the land, and percolate by the fissures, &c., to the drains, but 
runs on the surface, or between the tilth and the floor upon 
which it rests, to the furrow over the drain, to filter into it tlirouf/li 
the fillin(j-in, whatever plan may be adopted to facilitate the 
infiltrati(m of the Avater to the drains, it will fail. From exten- 
sive experiments which I have made in filtering water, I have 
found that, through almost any medium, it is less difficult to clear 
20 gallons of water holding siliceous or earthy matter (free from 
clay) in suspension, than one gallon of water with pure clav 
held in suspension. From the results of these experiments, on 
examining imperfectly drained clay lands, where the water stood 
* The fissures in tenacious clay subsoil run perpendicularly from the 
surface, and are connected, as may be seen, on the surface, in dry weathei-, 
in every variety of form, Imt never run m a horizontal direction unless 
there is some admixture of other soil, or the bed of clay is very thin, so 
that a fissure runs horizontally between the clay and the floor upon which 
it rests. 
t An important point to be determined in the drainage of land is, in 
which way does tlae water enter the conduit of the drain, whether through 
theflliiiij-in or through the land; if through the ^^'///w/;-/?;, it enters at the 
top of the conduit, if through the land, at the bottom. In numerous ex- 
periments and observations which I have made, I liave always found the 
water enters the conduit on a level with the bottom ; and when I have 
directed the attention of experienced drainers to the subject, and alter 
they have made their observations, I have found in evcri/ imtance that the 
result of their observations was in accordance with my own, that upon 
well-drained land the water percolates through the land and enters the 
conduit on a level with the floor. 
