THE FARMER'S MAGAZINE. 



manj- gentlemen now present ave at least as well acquainted 

 as myself with what I am now about to state ; but never- 

 theless I must, for the purpose of clearing the ground, com- 

 mence by laying down elementary principles. Now what 

 is the difference, chemically, between a drained and an un- 

 drained soil ? An undrained soil is, I apprehend, not 

 simply a soil in which water is present, but a soil in wliich 

 water is present to an abnormal extent— to an extent that 

 will injure the vegetation. The question then arises, how 

 does an excess of water injure the condition of the soil? If 

 you have a large quantity of water very near the su'face of 

 the soil, that water by its evaporation produces cold ; the 

 land is, in consequence of being undrained, very much colder 

 than it otherwise would be; in other words, the average 

 temperature of the soil, throughout the year, is very much 

 lower than it would be, if the water did not approach so 

 near the surface. That is one case. We will take an- 

 other—that in which the water-level does not come to 

 the top of the land, but so near to it, that the mere capil- 

 lary attraction of the soil will bring the water to the 

 surface. Here you have a second case of injury from ex- 

 cess of water, though not so bad a one as the first. Now, 

 in order to illustrate what I mean by " capillarj' attrac- 

 tion," I Avill just set at work a little instrument which I 

 have on the table, the action of which will proceed while I 

 am speaking. I have here, in a glass tube, a quantity of 

 dry sand. The bottom of the tube is covered with a small 

 piece of linen, to retain the sand in the tube. I have also 

 a little cup containing water. I will now insert the bottom 

 of the glass tube in the vessel of water. You will observe 

 that the water rises through the pores of the sand much 

 higher than the level of the water m the cup. The power 

 which causes the water to rise is called " capillary attrac- 

 tion" — that is, the attraction of minute tubes. [The water 

 rose in the tube many inches above the level of the water 

 in the cup.] Now, what is styled "capillary attraction" is 

 simply the power which all soil has, under certain circum- 

 stances, of taking up water by attraction bej'ond the ordinary 

 level, into the pores of the soil itself. Capillary attraction has a 

 very important bearing on the question of drainage,a3 respects 

 both the depth and distance of collateral drains. I wish to 

 impress upon you this point — that, where the soil is exceed- 

 ingly fine, where the pores of the soil are very minute, 

 capillary attraction will raise the water much higher than 

 it will where the soil is of a gravelly and coarse character. 

 In the more porous soils, water will not rise so high as in 

 soils of an opposite description. It is a well-known fact 

 — a fact which might be exhibited by means of glass tubes 

 drawn out to different degrees of fineness — that the 

 finer the tubes or pores, the higher water will ascend in 

 them. It must, therefore, be borne in mind that the ca- 

 pillary attraction of the soil will necessarily exert a consi- 

 derable influence on its condition. This ought to affect 

 the judgment of evcrj' man who puts a drain into the land, 

 because, in proportion as the capillary attraction of different 

 soils varies in force and amount, so the modes of draining 

 those soils properly and effectually must vary likewise. 

 Another point of considerable importance is this— that, in 

 drained land, not only have you got rid of the evaporation 

 of the water from the surface of the soil, but the soil at the 

 surface, being warmed by the rays of the sun and by the 

 diffused heat of day, warms the water that falls on the 

 soil ; and that water, in passing downwards, leaves its heat 

 in the soil. You see, therefore, that, if a soil be capable of 

 deep drainage, the deeper the drain, within certain limits, 

 the greater will be the amount of soil heated by the water 

 that comes from the surface. There is a ver^' important 

 point relating to the distance of drains, upon which I shall 

 say a few words hereafter. Another effect presents itself 

 here— namely, that, after the water has entered the soil, 

 the air mu'it follow it. So that you have two cou'ses of 

 action. You have the water heated, particularly in 

 yammer weather, passing don-nwards, and warming the 

 soil ; and you have the warm air following afterwards, and 

 also warming the soil. Besides that, the drainage has a 

 distinct action in disintegrating the mineral matters of the 

 soil for the purposes of the plant, and in oxidizing the 

 vegetable matters, and furnishing means by which the pro- 

 cess of vegetation may take place more rapidly than it 

 otherwise would do. Thus good drainage replaces rank 

 weeds and grasses by grasses of finer quality and more 



nutritious properties. [Mr. Ne.sbit here illustrated the fact 

 of the retention of heat in soils by pouring heated water on 

 some soil in a glass vessel. The hot water, after passing 

 through eighteen inches of soil, issued therefrom quite cold, 

 the heat of the water being retained in the soil] It is 

 quite clear that, in such a case, the heat left in the soil 

 must have warmed the roots of the plants growing in that 

 soil. I am obliged of course to use, in performing this ex- 

 periment, a rather coarse species of soil, because I must 

 make, as it were, a week's rain pass through in a very 

 short space of time. In the soils themselves to which I 

 have been referring, the action is, of course, not so rapid ; 

 but the principle is the same. 



Mr. Mechi : The fall of rain in the first instance expels 

 the air ? 



Mr. Nesbit: When water falls on dry and porous soils, 

 it first, as it descends, drives out the air, and is then itself 

 followed by air from above. The question of deep and 

 shallow drainage is one which you will have to determine, 

 in each case, upon its own merits (Hear, hear). The expe- 

 riments which I have to exhibit will, however, evince 

 clearly that there is no one decided depth, and no one de- 

 cided width, at which it can be laid down as a rule that all 

 draining should be carried on, but that draining must vary 

 according to the circumstances and condition of the soil 

 (Hear, hear). What I wished to do was to illustrate the fact 

 that when water is heated at the surface, and then passes down- 

 wards to a drain below, it issues, in spring and summer, very 

 much cooler. 



A Member : Is that regular soil? 



Mr. Nesbit: It is a gravelly soil. You see, then, very 

 clearly that, eo far as chemical principles are concerned, we 

 have here the passage of the water through the soil and the 

 alternative passage of air ; and thus we have the irrigation and 

 the aeration of the soil accomplished in the most beneficial 

 manner by means of drainage. If you now look to this illus- 

 tration of capillary attraction, you will see that the water has 

 risen some four or five inches, in apparent opposition to the 

 principle of gravitation. Well, now, before I proceed to speak 

 of simple, regular drainage at so matiy feet distant, such 

 drainage as uniformly-pervious soils must require, let me refer 

 to a few facts in connection with the drainage of springs, 

 and of certain particular soils in various localities. The 

 case of the drainage of springs is one that ought, perhaps, to 

 be considered separately from that of the ordinary gridiron 

 draining, as it has been termed ; but it is very often found 

 that, by one or two drains, one can set free a very large tract 

 of land from the water that comes in from a higher level. I 

 have here [referring to some diagrams suspended against the 

 wall] illu^tr'.tions of a few cases to which I wish to allude. The 

 first rase tn which I shall allude is the most ordiuary one. 

 It isoue which very fr.quently occurs in the West of England. 



[Diagram No. 1.] 



Here you have the rocks themselves upon which the vegetable 

 soil rests stratified very nearly vertically (as represented in 

 Diagram No. 1); jou have a pan g,(], almost impervious to 

 water ; and upon that pan you have vegetable earth. Now, 

 instead of this soil requiring to be drained in the ordinary way, 

 the subsoil plough is, in fact, all that is wanted. If the line rj y 

 be cut through by the subsoil plough or otherwise, at proper 

 intervals, the land will be drained by the percolation of the 

 water through the fissures of the rock. It must be recollected 

 that the plough must pass transversely to the stratification. 

 You just plough the subsoil, so as to break the pan; and if 

 my friend Mr. Robert Smith were here, he would tell you that 

 a very considerable portion of Exmoor has been drained by 

 him in this manner. Where the upper surface of the nearly 

 vertically-stratified rock is too deep to be touched by the sub- 

 6oil plough, the simple brcakiog-up of its outcrop at suitable 



