Now we have still to consider inundations. As defensive means and also as phenomena in the natural world they have unquestionably the nearest resemblance to morasses.
They are not common certainly; perhaps Holland is the only country in Europe where they constitute a phenomenon which makes them worth notice in connection with our object; but just that country, on account of the remarkable campaigns of 1672 and 1787, as well as on account of its important relation in itself to both France and Germany, obliges us to devote some consideration to this matter.
The character of these Dutch inundations differs from ordinary swampy and impassable wet low lands in the following respects:
- The soil itself is dry and consists either of dry meadows or of cultivated fields.
- For purposes of irrigation or of drainage, a number of small ditches of greater or loss depth and breadth intersect the country in such a way that they may be seen running in lines in parallel directions.
- Larger canals, inclosed by dykes and intended for irrigation, drainage, and transit of vessels, run through the country in all possible directions and are of such a size that they can only be passed on bridges.
- The level of the ground throughout the whole district subject to inundation, lies perceptibly under the level of the sea, therefore, of course, under that of the canals.