14 PERMANENT AND TEMPORARY PASTURES 



main stream has retired sufficiently to enable this water to 

 flow if only a channel were provided. 



The manner in which drainage should be carried out in 

 any particular case depends on soil, climate, and other con- 

 siderations. These conditions must of course be taken into 

 account, but they concern the details and not the principle of 

 the work. The difference between the rainfall in the eastern 

 and western counties,^ or between the West of England and 

 Ireland, will regulate the nearness of the lines of drains and 

 the size of the pipes. But these differences do not touch 

 the main question, whether to drain or not to drain. Soils 

 which rest upon a porous subsoil certainly do not need drain- 

 ing. Other land may be retentive, and yet lie so high, or at 

 such a steep inclination, that the water is discharged with 

 sufficient rapidity without artificial aid. Indeed, draining 

 may always be considered unnecessary where the best natural 

 grasses grow luxuriantly. With these exceptions all clay 

 lands, whether the clay is only in the subsoil or rises to the 

 surface, and all peat lands, whether the peat has clay beneath 

 it or not, and in fact all land which is habitually saturated with 

 water, must be effectually drained before a pasture of any 

 value can be established. 



The prejudice which occasionally exists against the adop- 

 tion of a system of drainage can generally be traced to some 



^ The following statistics, compiled from the Ileports of the Meteorological Office, 

 show the difference in rainfall which occurred during 1906 in various districts in Great 

 Britain : — 



* England (Highest rainfall)— Counties of Somerset, Dorset, 



Devon, and Cornwall 36-56 inches 



„ (Lowest rainfall) — Counties of London, Middlesex 



and adjacent on the North .... 22-32 ,, 



Scotland — Northern and Western Counties . . . 52-98 ,, 



,, Eastern Counties 35-56 „ 



Wales 42-46 „ 



The case named by Professor Ansted in his Physical Geography is still more 

 remarkable. He says : ' At Seathwaite the fall is 127 in., and a few miles off, at 

 Bishop's "Wearmouth in Durham, on the other side of the moors, it is only 17 in.' 



