486 



NEW ENGLAND FARMER. 



Oct. 



you can easily conceive that the loss of heat by 

 the evaporation of a comparatively inconsidera- 

 ble portion of this must involve a great cooling 

 of the land. If thirty inches of rain were evapo- 

 rated in this way, it would need 1 cwt. of coal 

 per hour per acre through the year to make good 

 the loss of heat sustained in this way ; a quanti- 

 ty which, in Dr. Arnott's hands, would give us 

 an Italian climate. The quantity, however, ac- 

 tually lost by evaporation is of course nothing 

 like this ; a great deal of water finds its way 

 throuiih the land. The water supply of all our 

 springs and wells, if that were known, would in- 

 dicate its quantity for the island. A great deal 

 escapes in flood times by running over the sur-j 

 face, and a great deal now finds its way out of 

 drains after percolation through the soil. Not- 

 withstanding these causes, however, and notwith- 

 standing the extremely irregular character of the 

 rain-fall, the loss by evaporation must be very 

 considerable. Dalton measured the quantity of 

 M'ater escaping from two rain gauges, one of an 

 ordinary kind, and the other filled three feet deep 

 with earth, and he found that of thirty-three 

 inches of rain which fell per annum as indicated 

 by the one, only eight and-a-half passed through 

 that quantity of earth as indicated by the other, 

 and he concluded therefore that the difference 

 between the two — twenty-five inches, or three- 

 quarters of the whole annual fall — escaped by 

 evaporation. 



Mr. Dickinson, of Abbot's Hill, near Kings 

 Langley, has for several years copied Ualton's 

 experiments, with results somewhat dift'erent from 

 his ; finding that of twent^'-six inches per annum 

 fifteen were evaporated, while as much as eleven, 

 rather more than two- fifths of the annual rain-fall, 

 passed through the soil. His results, however, 

 probably exaggerated the quantity of the rain- 

 fall which in general passes through the land, for 

 it is plain that earth loosely placed in Dalton's 

 gauge is much more likely to transmit the rain 

 which falls upon it than the same depth of earth 

 can be in ordinary circumstances, the lower hnlf 

 at least never having been disturbed since the 

 Deluge. And in fact the attempt of Mr. Milne 

 HomiC to ascertain the truth upon this point, by 

 measuring the water actually escaping from the 

 mouths of drains in a field of a given extent 

 (though it on the other hand was liable to an op- 

 posite error, because it could not take account of 

 what went through the land altogether to feed 

 the wells and springs of the neighborhood,) leads 

 to the conclusion that a much less quantity of 

 water than either Dickinson or Dalton indicates, 

 passes through the land in the course of the 

 year. And it would appear from this that the 

 loss of water by evaporation even in well- 

 drained soils is considerable, and therefore that 

 the loss of heat by evaporation is to a great ex- 

 tent unavoidable. 



3. — Let us now, however, consider what water 

 does by percolation ; and its efiects here we must 

 do little more than enumerate. They are short- 

 ly these : It carries the temperature of the air 

 into the soil, a thing the possible injury of 

 which, as in autumn and winter, when the air is 

 colder than the soil, is as nothing compared with 

 the benefit of it in spring, when the air is warmer 

 than the soil, and when the advantages of early 

 growth are great. The most important experi- 



ments which we know, proving the influence of 

 drainage on the temperature, are those described 

 by Mr. Stephens in his exceedingly instructive 

 little book descriptive of the Marquis of Tweed- 

 dale's operations at Yester Mains, where, the 

 temperature of soil being 40 deg. in itsundrained 

 state, the cutting of a drain near it and the set- 

 ting in of a current through it, raised its temper- 

 ature Li deg. in six hours. 



Another eS'ect of water percolating through 

 the land is seen in the introduction to it of the 

 atmcsphtric elements which it holds in solution. 

 The carbonic acid by its operation on the alkalies 

 and alkaline earths is a powerful solvent and 

 disintegrator, and the oxygen keeps in check the 

 deoxy dating efi'ect of vegetable matter in the 

 soil, which in its absence tends to reduce the 

 higher state of oxydation of the iron present in 

 the soil into the lower state, when it does mis- 

 chief by forming with acids in the soil soluble 

 salts injurious to vegetation. 



But the main purpose served by water during 

 its percolation through the land is that of feeder 

 of the plants. A fertile soil, cultivated so as to 

 exhibit its fertility in the most profitable manner, 

 has growing upon it crops whose habit and spe- 

 cific character are adapted to the climate in which 

 they are placed, and to the character of the soil 

 itself — it yields these crops in the order in which 

 each succeeding to the cultivation of its prede- 

 cessor shall find the soil, chemically as regards 

 its contents, and mechanically as regards its tex- 

 ture, and practically as regards consequent clean- 

 ness of the land and the fitness of their respective 

 times of cultivation to one another, in the best 

 condition for the supply of the wants of the crop 

 in question — it is annually manured a- d culti- 

 vated so as best to meet the current wants of the 

 plants cultivated on it — but it is especially de- 

 pendent for all its powers to bring these crops to 

 a fruili'ul maturity upon the fact that there is 

 during every shower and after every shower of 

 rain a continual current of water and a current 

 of air throughout its substance, not too rapid, 

 lest its soluble parts should be washed to waste ; 

 indeed, it is hardly possible to be too slow; slow 

 enough, however, to dissolve from the soil what- 

 ever it contains of food for plants, and fast 

 enough to be continually bringing fresh supplies 

 by every mouth which the absorbing extremities 

 of the roots of plants present. 



All these puiposes of warming the soil, of in- 

 trcdvcivg svhsiances within it which shall operate 

 chemically upon the mineral and other matters 

 within the soil, and of conveitinr/ the 6oil into an 

 (fficient vehicle of the matters which it contains, 

 are answered by the percolation cf water through 

 the soil. You must not think, then, of drainage 

 as being a contrivance for getting rid of water as 

 an enemy from the land ; nor must you think of 

 a wet and ill-drained field f.s being merely an il- 

 lustration of the injury done by water in excess, 

 as it is called. Water need hardly ever be an 

 enemy, and need hardly ever be in excess. 

 Drainage is a contrivance for making use of it 

 as a friend, and an ill-drained field is an illustra- 

 tion of the mischief done by water, whether 

 there be little of it or much, when not in motion. 



It is well, however, to consider the mischief 

 that may be done by the percolation of water. 

 If, as it moves through the soil, it contains the 



