60 OUTLINES OF FORESTRY. 



" On level surfaces of rock the weathered crust may remain 

 with comparatively little rearrangement until plants take root 

 on it, and by their decay supply organic matter to the de- 

 composed layer, which eventually becomes what we term 

 'vegetable soil.' Animals also furnish a smaller proportion 

 of organic ingredients. Though the character of the soil de- 

 pends primarily upon the nature of the rock out of which it 

 has been formed, its fertility arises in no small measure from 

 the commingling of decayed animal and vegetable matter with 

 decomposed rock. 



" A gradation may be traced from the soil downwards into 

 what is termed the ' subsoil,' and thence into the rock under- 

 neath. Between the soil and the subsoil a marked difference 

 in colour is often observable, the former being yellow or brown, 

 when the latter is blue, gray, red, or other colour of the rock 

 beneath. This contrast, evidently due to the oxidation and 

 hydration especially of the iron, extends downwards as far as 

 the subsoil is opened up by the rootlets and fibres to the 

 ready descent of rain-water. The yellowing of the soil may 

 even be occasionally noticed around some stray rootlet which 

 has struck down farther than the rest, below the general limit 

 of the soil." 



logical Survey of Great Britain and Ireland, etc., etc. London : 

 Macmillan & Co., 1882. Pp. 971. 



