other particles of water, and consequently leave them and ascend the glass. The height 

 to which they will ascend is probably in the inverse ratio of the diameter of the tube. 



\yhen a soil, especially a retentive one, is underdrained, the water as it percolates 

 through it leaves innumerable small pores; it becomes like a sponge — a reticulated 

 mass of fine tubes. These tubes, when the surface is wetter than the subsoil, carry 

 down the water to the drains below ; and when the surface is dryer than the subsoil, as 

 it is in a drouth, these tubes carry up the water to the roots of plants. Underdraining 

 is not built on this theory, but the theory is founded on the practical results of under- 

 draining, and will the more commend itself to practical farmers. 



Plants can take their food only in a state of dilute solution. They can not live and 

 grow without a constant supply of fresh water. Stagnant water is exceedingly delete- 

 rious ; no fact is better demonstrated than that agricultural plants can not thrive, how- 

 ever well manured, so long as their roots are surrounded with stagnant water. The 

 necessity for underdraining rests on these three facts. Not only does underdraining 

 remove all excess of water, and supply it when deficient, but it equalizes the temperature 

 of the soil. In the spring and fall, when a warm soil is so much needed for the germ- 

 ination and maturation of seeds, the thermometer shows that an underdrained soil is 

 several degrees warmer than one that is not drained ; while in very hot weather, the case 

 is exactly the reverse of this. It is a well known fact that vegetation starts much earlier 

 in the spring, and continues later in the fall, on a drained than on an undrained soil. 



But beside the beneficial mechanical eflect on the soil, imderdraining has gi'eat chem- 

 ical action. The removal of stagnant water and the free admission of air in its stead, 

 accelerates the disintegration of minerals as well as the decomposition of organic matter 

 in the soil, rendering them both available as food for plants. Again, the rain, as it falls 

 and filters through a well drained, loamy soil, carries to the plants one of the most 

 needed and expensive of all the constituents of cereal crops. Our readere need not be 

 told that we mean ammonia. In our article on the Plowing in of Green Crops, in the 

 June number of 1852, will be found some of our reasons for thinking ammonia the most 

 valuable and necessary ingredient in all wheat soils. The rain water which falls on an 

 acre of land in a year, is estimated to contain over 100 lbs. of ammonia, or sufficient for 

 the growth of 17 bushels of wheat. The recent experiments of Way and Thompson 

 have shown that when ammonia is filtered through a soil containing a good porportion 

 of chiy, the ammonia is retained in the soil, and the water passes through free from it. 

 Does this throw no light on the cause of the increased crops following thorough under- 

 draining? The other causes we have mentioned are merely concomitants. It is well 

 known that mechanical texture of soil, moisture, heat, eJectricity, and sunshine, indis- 

 pensable as they are, will not grow crops unless the required constituents of plants are 

 present in the soil in proper quantity and quality. Does it throw no light on the 

 biMU'tieial effects of summer-fallow on heavy clays. To our mind it gives a satisfactory 

 explanation to these questions that is consistent with experience and well established 

 srientilic principles. It is simply, that the ammonia contained in rain water is retained 

 I'v the soil as the water Slowly percolates through it to the drains beneath. In the case 

 of a summer-fallow, the constant plowing, dragging, &c., divides the particles of the soil, 

 for the first few inches in depth, so fine that they are capable of retaining all the ammo- 

 nia brought to the soil during the year on which it is summer-fallowed. This ammonia 

 it n!tains for the succeeding wheat crop. But even in this case, if the land needs drain- 

 ing, (imd what land that should be summer-fallowed does not?) the full benefit is not 

 obtained ; ail the rain which fiUls in the spring, autumn, and winter, when the soil is 

 fully saturated, passes oft" in surface water, the ammonia it contains along with it, together 

 with a considerable quantity of matter taken from the soil in mechanical solution. 



The co.st of underdraining is the most potent argument against its adoption. Thirty 

 . doHa'rs is consideiable money *to invest on an acre of land ; but it must be remembered 



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