THK SOIL OF THE FAIiM. '393 



into a lake, and sinking to the bottom, continues a process which, in the 

 course of time, will gradually convert the lake itself into an alluvial 

 tract. 



Voi.< AXH: ACTION. It is well known that lava slowly crumbles into a 

 fine fertile clay. The flanks of Vesuvius and ^Etna are clothed with vine- 

 yards and olive gardens, and the effects of volcanic action are observable 

 in certain parts of our own country, where the active cause has long 

 ceased to operate. The formation of a soil from lava is effected, first by 

 the rapid cooling of the surface of the molten stream, which speedily 

 cracks into a cindery or scoriaceous porous mass, and this gradually yields 

 to the influences of moisture and changes of temperature, and forms a 

 soil. 



PEAT. There still remains a process by which a considerable class of 

 soils has been formed, differing very widely from those which have been 

 described. It is that of vegetation or growth. All peats have grown. 

 and their history is sometimes traceable from its commencement. Peat 

 soils occur only in moderate and high latitudes, but form an important class 

 of cultivated soils in some countries, a very large proportion of Ireland 

 that country containing 2,800,000 acres of peat, and large tracts in 

 France, Germany, Russia, and all north European countries. Peats fre- 

 ntly rest upon clay, and the history of their formation will be usually 

 found to have been a modification of the following typical account. 



A forest or tract of brushwood is overblown or levelled by some severe 

 wind or flood. The consequence is an interruption of the natural drain- 

 age of the locality, and tin- inducement of a wet and spongy condition of 

 favourable to the growth of many species of spin t<f num. These plant-* 

 have the pr<>p.-rty of throwine; up Ml ' xv s -'x>ts while the lower extremities 

 are decayim:. I'eaty matter also appears to be precipitated from w. 

 at tin- 1; >int, when organic matter held in solution falls to the 



bott' 



IM i [TAB Y) AND TKANSIM.KTED SOILS. We are now aMe 



to divide all soils into t* tea, First, those which may be said 



'. or t<> remain in the position wl^-re they were originally 



mple, take the thin while soils of the rpper ( 'lialk 



whi pond clo>,-]y in character with the OOmpftd chalk rock be- 



bh. They are white, abound in flint and .-\ id-ntly 1- 



Ik, and are pr,perly formed chalk soils. So also the clay, of the 

 Id, and of the ( Kf..rd clay, the red Boill >f the New and 



and the brashy " lig "f th,. I all 



.,f the nature ,f t 1 :.- un-ler!yii. distinctly influenced 



