RECLAMATION OF THE SOIL. 23 



a shallow-rooted species and being satisfied with moderate 

 returns. 



2. Treatment of Swampy Ground generally. 



Each species thrives best with a definite degree of 

 moisture in the soil at all times of the year.* That 

 degree differs considerably in the case of the several 

 forest trees ; while some like moist and even wet soil, 

 others will not flourish in such localities, and none of 

 them in stagnant water. It follows that an excess of 

 moisture over and above what is suitable for a given 

 species must be removed, before a wood is started. The 

 method of doing this depends on the cause of the excess 

 of moisture. 



A locality becomes swampy if it receives more water 

 than can be disposed of by evaporation, filtering into the 

 subsoil, or surface drainage. An excess of water may 

 be due to excessive rainfall, inundation, underground 

 currents, or springs ; in the first two cases the swampi- 

 ness may be only temporary. The natural draining 

 away of the excess water may be impeded by an in- 

 sufficient local gradient, by an impermeable soil, or by 

 both combined, the last being the usual case. 



Before removing the surplus water from a swampy 

 piece of ground, the expense and the effect of drainage 

 on the surrounding lands should be carefully considered. 

 The cost is, as a rule, considerable, and sometimes pro- 

 hibitive : draining a swamp may seriously reduce the 

 necessary degree of moisture of adjoining areas, especially 

 in a hilly country ; the level of underground water ; 



* See pages 130 and 139 of Volume I. 



