25 



composed of or underlaid by coarse sand or gravel. They too 

 admit of the highest degree of aeration, but have little capillary 

 power ; whence it appears that it is the extremely porous soils of 

 whatever material — that is, those best adapted for aeration — 

 that suffer most in time of drought. 



Well-drained soils, then, are not so effectively benefited in a dry 

 time through the moisture which they absorb from the air as through 

 that which they permanently retain below the effective action of 

 evaporation and above the water table, supplemented by that 

 absorbed from below through capillary attraction. 



Such soils, whether too exclusively of peat or of coarse sand, 

 may be improved by processes which tend to compact them so as 

 to reduce the size and volume of their pores, thus diminishing 

 aeration and increasing the moisture obtained by capillary attrac- 

 tion. In the case of well-drained peat soil heavy rolling after sow- 

 ing or planting is often an effective aid to the germination of the 

 seed. In dry times grass seed sown on such land will often be 

 found to sprout and grow in the deep foot-prints of men and horses, 

 while elsewhere no growth may appear until copious rain has fallen. 

 Another method is by increasing the compactness and weight of 

 peat by adding to and mixing with it either fine sand, clay or marl, 

 or a combination of them, which will also improve its general 

 chemical and physical qualities ; while the excessive porosity of 

 sandy soils may be improved by the application of clay or marl and 

 decomposed muck or peat, the fine particles of which, filling the 

 coarser pores of the sand, tend to retard evaporation and to pro- 

 mote the absorption of water from below. 



How TO DRAIN Land. 



Under-drainage works cayi, and if rightly done to ill be, strictly 

 speaking, j)ermanent improvements. The construction of farm 

 buildings, roads, walls and fences, though usually classed as such, 

 are of a transitory and ephemeral character, compared with a well 

 planned and thoroughly executed system of tile drainage. 



That a drain may be permanent in its life and action, it must 

 be so planned and constructed as to let the tvater in and keei) the silt 

 or earthy matter out. An open ditch may do the first admirably 

 for a time, but soon fills up with the undermining and caving-in 

 of its banks, and by the in-washing of loam and organic matter 

 by the flow of surface waters into it. A stone or " blind" drain 

 may admit water freely for a time, and conducts it fairly well 

 where a considerable inclination or fall to a suitable outlet is 

 practicable ; but when laid (as such drains usually must be) in 



