On Drainivg. 
265 
which was sown with turnips. The drains were found in many 
places to be completely stopped with very fine roots in October. 
It seems to be difficult, indeed impossible, to pronounce from 
what plant these roots proceeded. I sent specimens of them to 
Professors Lindley and Daubeny, who kindly examined them, but 
neither of these botanists is able to decide on the parent plant, 
to which the roots unfortunately were not traced when the pipes 
were taken up. The drains were shallow, not exceeding 2 feet 
6 inches deep anywhere. The boggy soil contained many sorts 
of weeds, as crowfoot, coltsfoot, rushes, and docks, of which there 
was abundant evidence when I was on the spot some weeks after- 
wards. The pipes sent me contained much earth, which had got 
into them, with the roots, and I understand that several of the 
pipes were almost stopped with soil alone, but it is also true that 
others, in which the roots had worked, were free of earth. From 
all the evidence I could collect on the spot, I am disposed to con- 
sider this stoppage by roots to have originated in bad laying of the 
pipes by the farmer, and insufficient depth in a very foul piece of 
land. It is however a case of warning, and one to excite vigilance 
of observation. I have now a drain laid deeply in the same soil 
with pipes collar-jointed, and other drains to test any difference in 
future action and phenomena. 
It is important that every case of the stoppage of drains from 
the entrance of roots should be well investigated; but we may 
rest quite satisfied, from our long experience of under-drainage, 
that instances of this evil will only be of casual, and, probably, of 
merely local occurrence. With the exception of the one case 
cited, I have not heard of the occurrence of a single case of root 
stoppage in pipes ; but it is evident that if the roots of weeds or 
cultivated plants were in the habit of preferring to burrow in a 
drain rather than in the bed of the soil, a pipe drain would be as 
liable to be choked as any other form of drain. 
I will now refer to one or two natural aids to drainage. 
Besides the porosity of soils, by which they receive and part 
with water more or less readily, according to their openness or re- 
tentiveness, there are other adjuncts or means auxiliary to its recep- 
tion and discharge. It has not occurred to me to excavate many 
clay soils for drains, in which there are not perceptible what expe- 
rienced and observant drainers aptly call water veins. The clay is 
divided, as it were, into plates, masses opening or parting from each 
other like the leaves of a book, between which, thin as the vein is, 
an evident passage of water has taken place. These partings may 
have been originally occasioned by vertical cracks from the surface, 
which have never entirely closed again, and so served to conduct 
away some of the rain water to more porous and absorbent strata. 
It is a matter of fact that in all clays in which these water veins 
