348 



FARMERS' REGISTER. 



[No. 6. 



which have attended them, which will clearly 

 prove the great advantages to he derived from an 

 improvement that has now become much more 

 generally known and appreciated, mid is daily 

 gaining ground, not only in this country hut in 

 others — indeed there can be no doubt that, in a 

 lew years, it will be put in practice in all situations 

 where it is eligible. 



General principles of irrigation. 



To investigate, by observation or experiment, 

 the processes of nature is the object of physical 

 science: to imitate or regulate these processes is 

 the object of art. 



It is apparent to the most superficial observation, 

 that the banks of rivers, which are overfloived oc- 

 casionally, and the places contiguous to springs, 

 over which their waters continue to flow, are ever 

 covered with a conspicuous verdure of the sweet- 

 est grasses, while stagnant water converts the 

 land on which it lies to marsh, productive of no- 

 thing but coarse and unpalatable aquatic plants. 



To imitate this process of nature constitutes the 

 leading principle of the art of irrigation. 



Water is brought over the land in a constant 

 current, so gentle as not to endanger the tearing 

 up of the soil; and, at the same time, is all dis- 

 charged, so as to permit none of it to become stag- 

 nant; and, to gain these purposes, the land must 

 all be formed into a proper shape, both lor admit- 

 ting and discharging the water. 



In this, as in every other art, long practice leads 

 to perfectness; previous errors are thus detected 

 and amended, and new improvements are sug- 

 gested and brought to the test. ' 



The agency of water in the process of vegeta- 

 tion has not, till of late, been distinctly perceived. 

 Dr. Hales has shown that, in the summer months, 

 a sun-flower, weighing three pounds avoirdupois, 

 and regularly watered every day, passed through 

 it or perspired twenty-two ounces each day, that 

 is, half its weight. Dr. Woodward found that, 

 in the space of seventy-seven days, a plant of 

 common spearmint increased seventeen grains in 

 weight, and yet had no other food but pure rain 

 water; but he also found that it increased more in 

 weight when it lived in spring water, and still 

 more when its food was Thames water. The 

 next most important ingredient to the nourishment 

 of plants is earth, and of the different earths the 

 calcareous seems the most necessary, as it is con- 

 tained in rain water, and, absolutely speaking, 

 many plants may grow without imbibing any 

 other. Earths enter into plants in a state of solu- 

 tion when suspended in water in a state of divi- 

 sion, as minute as if they really had been dis- 

 solved; that silicious earths may be suspended in 

 such a state of division appears from various ex- 

 periments, particularly those of Bergman, who 

 found it thus diffused in the purest waters of 

 Upsal. 



One mode of its operation is, indeed, sufficient- 

 ly obvious. When brought over a meadow in 

 such a gentle current as to allow it to deposite 

 sediment, but, at the same time, so as never to 

 stagnate, the sediment deposited from the water 

 in its filtration through the grass must greatly en- 

 rich the soil.* And hence much more efficacy 



* All rivers, from the least to the greatest , waft 

 earth to the sea, and that in proportion to their magni- i 



may be expected from the waters of the large ri- 

 vers, draining extensive tracts of rich improved 

 soils, than from springs which receive no wash- 

 ings from surrounding lands, or from rivers run- 

 ning through tracts of mere mountainous pastoral 

 districts of poor and unimproved soil; although, 

 even in suen districts, considerable quantities of 

 enriching sediment may be expected from the wa- 

 ters of such rivers, if care is taken to have the 

 meadow in a proper state for receiving the waters 

 of the first flood after summer, which will wash 

 down and carry along with them the droppings 

 fallen from animals grazing upon the tracts of 

 country which such rivers drain. 



Another mode of the waters operation upon a 

 meadow, is by protecting the grass plants from 

 the effects of the winter frosts: for it is evident 

 that water req.iires more severe frost to freeze it 

 when in a current than when in a stagnant state; 

 and it is equally obvious that fluid water retains a 

 higher temperature than ice or hard frozen earth. 

 So long, then, as the frost is not so severe as to 

 prevent the water from maintaining its currency 

 over the meadow, the grass plants will be main- 

 tained in a higher degree of temperature than if 

 exposed uncovered to the air. 



It would appear, then, that irrigation acts upon 

 the vegetation of the irrigated meadow chiefly, I 

 should presume, from the deposite of manuring 

 sediment; in the next place, by shelter afforded to 

 the plants against severity of winter frost, and 

 from the decomposition which the water under- 

 goes in filtering through the grass. 



The best effects from irrigation may therefore 

 be expected when the irrigator can obtain his wa- 

 ter from the larger rivers, draining a large tract of 

 fertile and improved soils, or from those streams 

 which receive the drainings of great towns. Con- 

 siderable improvement may, nevertheless, be ex- 

 pected from waters which drain considerable 

 tracts of mere unimproved pasture lands of infe- 

 rior soil, which, at any rate, will afford winter 

 shelter; and, if advantage is taken of the earliest 

 floods after summer, will yield also considerable 

 quantities of enriching sediment. Nor is the irri- 

 gation from mere springs to be neglected, in re- 

 gard to the smaller patches of land which they 

 are capable of overflowing — in as much as their 

 superior temperature to that of running water 

 longer exposed makes them capable of affording 

 warmer and more kindly shelter in winter — with- 



tude, velocity, and length of course, combined with 

 the nature of the soil which forms the beds and banks, 

 and with the rains, which, in proportion to their vio- 

 lence and the degree of slope of the higher grounds, 

 wash down the soil into the nearest stream. Mr. Rin- 

 nel says, that the quantity of alluvial soil wafted into 

 the sea by the waters of the Ganges, is a two hun- 

 dredth part of the whole volume, or 2,509,056,000 sol- 

 id feet per hour. The alluvial soil deposited by the 

 waters of the Nile, is the one hundred and twentieth 

 part of the whole volume, or 14,784,000 solid feet per 

 hour. 



The Mississippi deposites 8,000,000, solid feet per 

 hour, and the river Koangho, according to Barrow, 

 carries into the sea 2,000,000 solid feet of sediment 

 every hour. 



Although these facts had been witnessed for several 

 generations, it is but of late that the attention of phi- 

 losophers has been drawn to this subject. 



