136 GEOLOGICAL CHARACTER OF SOIL. 



lime the soil contained. The amount of vegetable and other organic 

 matter in a soil is found by drying the soil well upon paper in an oven, 

 then burning a weighed quantity in the air, and the loss is the organic 

 matter. In stiff clay soils the loss will be in part water, not wholly 

 driven off by drying. 



Geological Character of Soil. 



The character of sub-soil should always be examined ; and the sea- 

 son of the year at which the examination is made, whether dry or 

 moist, in spring or in summer, are also subjects of much importance 

 in purchasing or renting land. By digging down with a spade 18 in- 

 ches in various parts of the land, the sub-soil maybe known. In dig- 

 ging through the soil and sub-soil, we arrive at length, at a greater or 

 less depth, upon the solid rocks. In some cases these rise to the sur- 

 face, or very near it, and in others they are far below it. These rocks 

 are very unlike in character, composition and hardness. In one place 

 they are a sand stone, in others a lime stone, a slate or hardened clay, 

 etc. Any of these left exposed to the action of rains, frosts and 

 winds, a considerable time, are seen to disintegrate, crumble and waste 

 away, and the minute fragments form soil in which plants are seen to 

 spring up. Hence the soil partakes of the character of the rock. If 

 this be sand stone, the soil is sandy; if clny-stone or slate, it is more 

 or less stiff clay-soil ; if limestone, it is more or less calcarious soil, 

 and if these are mixed, it is a mixed soil. As the soil resembles the 

 rocks on which it rests, the conclusion is that the rocks at one time 

 were uncovered, and that soil is the result of the gradual wearing 

 away of the rocks. 



The position of the rocks accounts for the circumstance why large 

 tracks of land are of the same composition, oftentimes ; while in other 

 places it changes frequently in short distances. Rocks are distin- 

 guished as stratified or unstratified. The first lie over each other in 

 separate beds or layers, the second form hills, ridges, or mountains, 

 and consist of a solid mass. The position of rocks, as they may com- 

 monly be found, will be seen by this illustration : 



This indicates unstratified and stratified rocks laying horizon- 

 tally over one another, as at a b c d. The soil at 1 and 6 may 

 of course be different from that of the horizontal layers, and these 

 in turn may be different from each other. The small valleys, 234, 



