546 
SCOURING LANDS OF CENTRAL SOMERSET. 
less nutritious roots, green and fodder crops; whilst a scanty 
supply of manure on naturally poor soils tends to push on 
plants to early maturity. It is upon this principle that gar¬ 
deners act when they require to force flowers into early bloom. 
Again, the fact that the complaint ceases almost entirely 
after the first November frost finds a ready explanation by 
my views on the character of the herbage from scouring pas¬ 
tures. Like the unripe wood of our fruit-trees, the unripe 
young clover-leaves and grass-shoots in our meadows are 
killed much more readily or changed in composition than the 
older and more matured portions of the herbage. But as the 
immature young leaves and grass-shoots only have medicinal 
effects, the pasture becomes either altogether sweet after the 
first autumnal frost, or the evil is seen in a much more miti¬ 
gated form on land which scours during the summer months. 
It now 7 remains for me to point out how 7 it is that scouring 
land frequently does not bring the herbage to a sufficient 
degree of maturity. 
In the first place I would observe that lias-clays contain an 
excess of mineral food, and, being retentive even after drain¬ 
ing, they also often contain a large quantity of water. The 
excess of water and coldness of the soil retard the early deve¬ 
lopment of the herbage. The upland position of all hill- 
pastures, on which the evil generally preponderates, of course 
is also unfavorable to an early growth of the herbage. But, 
more than this, the peculiar tenacious character of the lias- 
clay subsoils on scouring land, the great depth of these clay- 
beds, and their near approach to the surface soil, tend to 
retard vegetation, and to make it very gradual during the 
colder and wetter months of the year. In many cases under¬ 
drainage, besides taking off the surface water, produces little 
alteration in the condition of the surface soil, for the simple 
reason that it is too thin, and the clay subsoil bed too tena¬ 
cious and too deep to be penetrated by the ameliorating 
influence of the atmosphere. 
During many months of the year such thin surface soils in 
hilly districts, after they have been drained, remain as cold 
and almost as wet as before. When the temperature of the 
air becomes more genial to vegetation, and the weather much 
drier than during the other and greater part of the yegr, the 
clay-land on the Polden Hills becomes sufficiently dry and 
warm to allow vegetation to make a start; and the abundance 
of mineral food in the land then rapidly pushes forward the 
herbage, and causes it to grow 7 with much luxuriance, espe¬ 
cially if the summer temperature is high, and just sufficient 
dew or gentle rain falls to keep the clay from cracking. On 
the hills, and on naturally cold, stifl land, this period of rapid 
