13 



being easily worked, and the clods knocked to pieces, the plough 

 also turns out the weeds, only that it is apt to disturb the roots 

 of trees in the neighbourhood, and the bullocks, injure the trees 

 themselves. 



EARTH AND SOILS. Earths are the production of the rocks 

 which are exposed on the surface of the globe, and soils are earths 

 mixed with more or less of the decomposed organized matter 

 afforded by dead plants and animals. Earth and soils therefore 

 must be as various as the rocks which produce them. The surface 

 earth, or that which forms the outer coating of the dry parts of 

 the globe, is formed by the detritus of worn off parts of rocks, and 

 rocky substances. Earths are therefore variously composed, ac- 

 cording to the rocks or strata which have supplied the particles. 

 Sometimes they are formed from slate rocks, as in blue clays ; at 

 other times from sand stone, as in siliceous soils ; and mostly of 

 a mixture of cjayey, slatey, and limestone rocks, blended in propor- 

 tions as various as their situations. In process of time the decay 

 of vegetables and animals form additions to the outer surface of 

 the earth, and constitute what are called soils. As soon as the 

 smallest layer of earth is formed on the surface of a rock, the 

 spores of Lichens, Mosses, and other Flowerless plants, which are 

 constantly floating in the atmosphere, and which have found 

 a resting place, begin to vegetate ; their death, decomposition, 

 and decay, afford a certain quantity of organizable matter, which 

 mixes with the earthy materials of the rock. In this improved 

 soil more perfect plants are capable of subsisting. These in 

 their turn absorb nourishment from water, and the atmosphere, 

 and after perishing, afford new materials to those already provid- 

 ed. The decomposition of the rock still continues, and at length, 

 by such slow and gradual processes, a soil is formed in which 

 even forest trees can fix their roots, and which is fitted to 

 reward the labors of the cultivator. 



Preparation of Garden Soil at the commencement of the hot season. 

 It is stated by Leibig, that the frequent separation and inter- 

 mixing of the granules of the soil during suitable weather is 

 beneficial to it chemically and physically, the surface soil has the 

 power of arresting and fixing a large quantity of plant food, 



