Each grass has its own special favourite amount of moisture. It likes to have its water at just one particular depth below the surface. Unfortunately there are not nearly enough sympathetic and careful observations of the preferences of each individual grass. A Danish author has worked out the facts in certain localities (Geest). Suppose first that the water-level of the wells, etc., is 6-1/2 to 9-3/4 feet below the surface. This suits the Meadow Poa grass (_Poa pratensis_) exactly. It will grow luxuriantly and flourish. Now suppose the weather is very wet, so that the water rises in the wells till they are three to four feet deep. The Roughish Poa (_P. trivialis_) prefers this moister soil, and it will grow so vigorously that it will kill out the other kind. If it is a season of very heavy floods, or if the drains become choked so that the water rises to within fourteen to twenty-five inches of the surface, then the tufted Aira (_Deschampsia caespitosa_) will kill out the other kinds and flourish abundantly. But if the water rises higher than this the marsh series comes in (see Chap. XVI.). So that the thirsty grasses of the meadow are helped or hindered in their fight for life by changes in the water away down in the soil below their roots. Even in Great Britain one can see distinct differences in very dry and very wet summers, but all these pastures, meadowlands, and hay-fields are, as we have already mentioned, as much due to man's forethought and industry as a factory or coal-mine. It is very difficult to realize this. The best way is to go to the National, or any other good picture-gallery, and look carefully at any landscapes painted before the year 1805. You will scarcely believe that the country as painted can be the land we know. Where is the "awful orderliness" of England? Where are the trim hedges? Where are the tidy roadsides and beautifully embanked rivers that we see to-day? As a matter of fact, until the great Macadam made good roads and the great Telford and other engineers built stone bridges, it was impossible to rely on getting about with carts and carriages. Gentlemen's coaches and wagons used to be literally stuck in the mud! Horses were drowned at fords, or died in their struggles to pull very light loads through mud which nearly reached the axles of the wheels (see Chap. XI.). Besides the change due to roads, fences, drains, and farm buildings, the very grasses themselves are growing unnaturally. The farmer has selected and sown what he thinks best. He is obliged to do so, because grasses vary so much. Some of them shoot up quickly and die after the first year. Others live for two years, whilst a great many bide their time, developing very slowly, and not reaching their full growth until the fourth or fifth year.