Fig. 51. Open chalk cultivated country, Isle of Thanet
The black soil of the fen districts and elsewhere is widely different from any of the preceding. It contains, as its colour shows, a large quantity of combustible material (Chap. V.), which has a great power of holding water. These fens are therefore very wet; until they were drained they were desolate wastes: you may read in Kingsley's Hereward the Wake what they used to be like in old days, and even as late as 1662 Dugdale writes that here "no element is good. The air cloudy, gross and full of rotten harrs[1]; water putrid and muddy, yea, full of loathsome vermin; the earth spongy and boggy; and the fire noisome by the stink of smoking hassocks[2]." But during the Stuart period wide ditches or drains were dug, into which the water could flow and be pumped into rivers. This reclamation has been continued to the present time, and the black soils as well as the others in the Fen districts can be made very productive.
We have seen that a change in the soil produces a change in the plants that grow on it. The flora (i.e. the collection of plants) of a clay soil is quite different from that of a sandy soil, and both are different from that of a chalk or of a fen soil. In like manner draining a meadow or manuring it alters its flora: some of the plants disappear and new ones come in. Even an operation like mowing a lawn, if carried on sufficiently regularly, causes a change. In all these cases the plants favoured by the new conditions are enabled to grow rather better than those that are less favoured; thus in the regularly mown lawn the short growing grasses have an advantage over those like brome that grow taller, and so crowd them out. When land is drained those plants that like a great quantity of water no longer do quite so well as before, while those that cannot put up with much water now have a better chance. In the natural state there is a great deal of competition among plants, and only those survive that are adapted to their surroundings. You should remember this on your rambles and when you see a plant growing wild you should think of it as one that has succeeded in the competition and try to find out why it has been enabled to do so.
[1] Harr is an old word meaning sea-fog.
[2] Hassock is the name given to coarse grass which forms part of the turf burnt in the cottages.
CHAPTER XI
HOW SOIL HAS BEEN MADE
Apparatus required.
The apparatus in Fig. 54. The under surface, of the lips of the beakers should be vaselined to prevent the water trickling down the sides.
It is not uncommon to find cliffs or crags in inland places, but they usually show one very striking difference from seaside cliffs. The seaside cliffs may be nearly vertical, but the inland cliffs are not, excepting for a little way at the top; lower down a heap of stones and soil lies piled against the face of the cliff and makes a slope up which you can climb. If you look at the cliff you can find loose fragments of it split off either by the action of freezing water (p. 83) or by other causes ready to roll down if sufficiently disturbed. So long has this been going on that a pile has by now accumulated, and has been covered with plants growing on the soil of the heap. Our interest centres in this soil; no one has carried it there; it must have been made from the rock fragments. When you get an opportunity of studying such a heap, do so carefully; you can then see how, starting from a solid rock, soil has been formed. This breaking down of the rock is called weathering.
