Book III. IRRIGATION. 655 



4055. But the principal efforts in watering lands have been made during the latter end 

 of the last, and beginning of the present century, in consequence of a treatise on the 

 subject by George Boswell, pubHshed in 1780 ; and various others by the Rev. Thomas 

 Wright, of Auld, in Northamptonshire, which appeared from 1789 to 1810. The practice, 

 however, has been chiefly confined to England, there being a sort of national prejudice, 

 as Loch has observed {Improvements on the Stafford Estates, ^c.j, against the practice in 

 Scotland, though its beneficial etFects may be seen as far north as Sutherland, where 

 rills on the sides of brown heathy mountains, never fail to destroy the heath plants 

 within Uieir reach, which are succeeded by a verdant surface of grasses. A valuable 

 treatise on the subject of irrigation in Scotland, by Dr. Singer, will be found in The 

 General Report of Scotland, vol. ii. p. 610. In England the best examples of water- 

 ing are to be found in Gloucestershire and Wiltshire. In our view of this subject, we 

 shall first consider the soils and situations suitable for irrigation, and next the different 

 modes of effecting it, known as flooding, irrigating, warping, irrigation on arable lands, 

 and subterraneous irrigation. 



SuBSECT. 1. 0/the Soils and Situations suitable for the purposes of Watering Lands. 



4056. The theory of the operation of water on'lands we have already developed. It 

 appears to act as a medium of conveying food, as a stimulus, as a consolidation of mossy 

 soils, as a destroyer of some descriptions of weeds or useless plants, and as the cause 

 of warmth at one season, and of a refreshing coolness at another. From these circum- 

 stances, and also from what we observe in nature, there appears to be no soil or situation, 

 nor any climate, in which watering grass-lands may not be of service; since the banks of 

 streams between mountains of every description of rock, and in every temperature from 

 that of Lapland to the equator, are found to produce the richest grass. One circum- 

 stance alone seeins common to all situations, which is, that the lands must be drained 

 either naturally or by art. The flat surfaces on every brook or river, after being covered 

 with water during floods, are speedily dried when they subside, by the retiring of tlie 

 waters to their channel. 



4057. The most proper soils for being watered are all those which are of a sandy or 

 gravelly friable nature, as the improvement is not only immediate, but the effects more 

 powerful than on other descriptions of land. There are also some strong adhesive sour 

 wet lands, such as are common in the vicinity of large rivers, which are also capable of 

 being improved by watering, but the beneficial effects are not in such cases so soon pro- 

 duced as on those of the first sorts, nor is the process so advantageous to the farmer, on 

 account of the very great expense to which he must, in many cases, be put to by previous 

 draining. There are some other lands, as those which contain coarse vegetable produce 

 tions, as heath, ling, rushes, &c. which may likewise be much improved by watering. It 

 must be kept constantly in mind in attempting this sort of improvement, that the more 

 tenacious the soil is the greater the command of water ought to be for effecting the pur- 

 pose, as a stream capable of watering fifteen or twenty acres of light dry land, would be 

 found to be beneficial in but a small degree when applied to watering half the same 

 quantity of cold clayey ground such as in their natural state abound with coarse plants. 

 On all soils of the last kind a considerable body of water is requisite for the purpose of 

 floating them in order to produce much benefit, and where that cannot be procured, this 

 mode of improvement will seldom answer the farmer's intention or be advantageous in 

 the result. 



4058. Smith, an experienced irrigator, supposes that *' there are only a few soils to 

 which irrigation may not be advantageously applied : his experience, he says, has deter- 

 mined, that the wettest land may be greatly improved by it, and also that it is equally 

 beneficial to that which is dry." {Obs. on Irrigation, ^c.) But that as many persons 

 unacquainted with the nature of irrigation may be more inclined to the latter supposi- 

 tion than the former, he explains the reason of wet land being as capable of improvement 

 from flooding as that which is completely dry before. It is that in the construction of all 

 water meadows, particular care must be taken to render them perfectly dry when the 

 business of floating shall terminate ; and that the season for floating is in the winter and 

 not the summer, which those who are unacquainted with the process have too 

 generally supposed. All peat bogs are certainly of vegetable origin, and those vege- 

 tables are all aquatic. It follows that the same water which has produced the vege- 

 tables of the bog would, under due management upon the surface, produce such grasses, 

 or other vegetables, as are usually grown by the farmer ; and he lias hitherto had reason 

 to think, that this may be considered as a general rule for determining the situation of 

 any experiments with water. The lands that permit of this sort of improvement with 

 the most success are such as lie in low situations on the borders of brooks, streams, or 

 rivers, or in sloping directions on the sides of hills. 



4059. The quality of the water, like that of marl or other manures, is supposed by 

 some to be a matter of the first importance ; but it is nov* fully proved, by the accurate 



