IRRIGATION. 141 



tied that simple water, without any admixture, is in itself a great 

 enricher of the soil, or perhaps, more properly, a great promoter 

 of vegetation. If the water of irrigation is charged with en 

 riching matters in a state of solution, its beneficial effects are of 

 course increased. Waters charged with mineral substances, 

 such as water strongly impregnated with iron from peat bogs, or 

 water from copper mines, is pernicious to vegetation, as any one 

 may see, who will visit the outlets of the copper mines of Corn 

 wall. It is established, likewise, that water in irrigation, in order 

 to produce its best effects, must not be suffered to stagnate upon 

 the land, but must pass in a steady progress over it ; and that 

 this progress should be comparatively gentle, and not sudden and 

 rapid. It is equally well established, that lands which it is pro 

 posed to irrigate, should be thoroughly drained, so that the water 

 poured upon the land should not be suffered to stand in the land, 

 nor upon it. The effect of stagnant water upon the surface, or 

 the complete saturation of the soil, is to change the nature of 

 the herbage, and to produce those grasses, which are coarse or 

 innutritions, in place of the finer, sweeter, and more healthful. 

 Yet it is not the mere transition of the water over the surface 

 that is to be sought. It is desirable to have it soak into the 

 ground, but not to remain there. Its speedy transition over the 

 surface is to be effected by the inclination of the land from 

 where it is received to the trench, furrow, or ditch, by which it 

 is to be carried off. Its passing into the ground, and finding a 

 speedy passage off, is to be effected by a system of thorough 

 draining and subsoiling ; for if the subsoil is impervious, the 

 irrigated field becomes converted into a marsh. One of the 

 most eminent farmers in Scotland, whose hospitality I had the 

 pleasure of enjoying, but whose death since that time is deeply 

 to be lamented, Mr. Oliver, of Lochend, near Edinburgh, 

 who had a large extent of meadow, irrigated by the sewerage water 

 from the city, found that, after his fields were thorough drained, 

 the benefit of the irrigation was greatly increased ; for by the 

 descent of the sewerage water into the soil, as well as over it, 

 the enriching portions of the manure in a state of solution were 

 carried to the roots of the plants. In the irrigated meadows of 

 the Duke of Portland, for its extent one of the most beautiful 

 and finished agricultural improvements which can be found, and 

 which I shall presently fully describe, he showed me, that por- 



