GENERAL PRACTICE. SOILS AND SUBSOILS. 31 



a decidedly injurious tendency, particularly in the case of fruit trees, which are 

 injuriously affected by the lower oxidation of the iron in the soil. Indeed, upon the 

 degree of its oxidation depends the usefulness or injurious effects of iron on fruits. 

 Stagnant water prevents the union of ammonia with iron, but l.y the higher oxidation 

 its affinity is restored and ammoniated oxide of iron results, this by the action of 

 sulphuric acid being converted into sulphates of iron and ammonia respectively, both 

 being useful fertilisers. In soils permeable to air the evil tendency of iron is counter- 

 acted through the higher oxidation consequent on the free absorption of oxygen from 

 the atmosphere, but in a water-stagnated soil this important result is not attained. 

 This injurious action of stagnated water is equally applicable to all the mineral ingre- 

 dients of soils, for it directly prevents their assimilation into plant food. It acts equally 

 disastrously on the organic elements. Vegetable and animal decomposing matters in 

 a soil where water is superabundant give out carburetted hydrogen, acetic, gallic, and 

 other acids, instead of carbonic dioxide and ammonia. The former are poisons, the latter 

 food; and as ammonia is composed of nitrogen and hydrogen, its absence means an 

 incalculable loss of the nitrogenic products so essential to healthy vegetation. Then 

 there is the important factor of temperature. Sun heat falling upon water-logged land 

 does not exert its genial influence in warming it and promoting the growth of plants ; 

 but, on the contrary, its power is restricted to evaporation, which deprives the soil of 

 an immense amount of heat, directly preventing the assimilation of plant food and its 

 profitable employment in the formation and maturing of fruit. Experiments have 

 proved that if a pint of water is evaporated from 100 Ibs. of soil the land is left ten 

 degrees colder than it would be if the water passed away by filtration, and it has been 

 computed that the heat thus lost per acre daily is equal to the consumption of 12 cwt. 

 of coal. Thus it will be seen how important is free drainage. 



"When the soil is drained efficiently through pipes at a proper distance and sufficient 

 depth, its condition is entirely altered. Water no longer stagnates. The sun's rays 

 have their full beneficial effects, and the soil is made warmer and better suited in every 

 way to the crops, as well as furthering and economising cultural operations. Bain passes 

 through drained soil freely, and with it air, carbonic acid, and ammonia. These having 

 tree access, a wholesome, abundant, highly nutrient dietary may be afforded, which 

 enables trees to make clean, healthy growth, and produce full crops of the best fruit 

 that the varieties are capable of bearing. Indeed, a new storehouse of nutrition is 

 opened to them by drainage. In stagnant soil, the growths of trees are soft through 



