APPENDIX. 



FORMATION AND GROWTH OF SOIL OR SURFACE-MATTER. 



WHEN land is first exposed above water, or from 

 under ice, it is devoid of soil. Soil or vegetable 

 mould may be earthy, sandy, or organic; it takes 

 years to form, but it increases much more rapidly 

 under some circumstances than others; the process 

 being due to the combined effects of meteoric action, 

 the growth and decay of vegetable matter, and the 

 operations of certain animals. 



All rocks, no matter how hard and tenacious, 

 will, in time, weather and disintegrate if exposed to 

 meteoric action; but the detritus formed may not 

 always remain to produce soil, for if the land slopes 

 sufficiently, all, as fast as formed, may be removed 

 by rain or wind, the latter force being even capable 

 of removing detritus from a flat surface, especially if 

 in exposed situations. Many rocks, such as doleryte, 

 dioryte, granyte, some limestones, &c., are physically 

 hard, while they are chemically soft ; others, such as 

 slates, schists, clays, &c., are physically soft, while 

 they are very little susceptible of chemical deconi- 



