J. J. Griffith 383 



Effects upon Physical Properties op Soils. 



Pastures on affected land almost invariably present an appearance 

 which is very similar to that of herbage growing on soils liable to suffer 

 from drought. It is reasonable to suppose that one cause is a deficiency 

 of moistui-e following an alteration in the mechanical composition of the 

 soil as shown in Table VI. But this parched appearance is also found 

 in pastures which have been contaminated but not altered in mechanical 

 composition. It was therefore considered desirable to determine the 

 water content of affected soils in dry weather. This was carried out by 

 taking a series of samples along a line stretching across affected and 

 unaffected land. The samples were packed in air-tight tins and the 

 percentage of moLsture determined with as httle delay as possible. 

 Table VIII shows the results obtained with sample.^ taken at various 

 dates during the summer months of 1914. 



Sections D and E of Table VIII show that contamination by means 

 of polluted river water may diminish the water-retaining capacities of 

 soils very considerably. This unfavourable influence is undoubtedly a 

 factor which affects the herbage very appreciably. As already shown 

 in Table VI contamination by means of river water often affects the 

 mechanical composition of soils very unfavourably. This alteration of 

 mechanical composition does not always lower the capacities of afl'ected 

 soils to retain water. For example, on flat land in some of the river 

 valleys the permanent water table is near the surface and, conseqiiently, 

 the affected soils, although they are much more open in texture, contain 

 nearly as much moisture as the unaffected soils even in very dry weather. 



Sections A, B and C of Table VIII indicate that soils contaminated 

 by means of leat water and surface drainage water have not been un- 

 favourably afl'ected as regards their capacities to retain water. But as 

 already stated, the herbage on this class of affected soil also appears 

 very Uable to suffer from drought. This may be due to circumstances 

 which diminish the water-absorbing capacity of plants growing on 

 affected land. For instance, root development is very hmited, see 

 Photographs "E" and "J." Also the roots are observed to be restricted 

 to the surface soil especially if the lower layers of the soil and the subsoil 

 contain much lead or zinc. 



