No, V.\ OF THK PHYSICAL. PRCr£RTIES OP THE SOIL, ^ 



No. V. 



OF THE EXAMINATION AND ANALYSIS OP SOILS. 



l'^. Silection of spe-Anieiis of soils. — In the same field different varieties of soil 

 often occur, and some r3commend that in collecting a specimen for analysis, 

 portions should be taken from diiferent parts of the field and mixed together, 

 by which an av3ragj3 quality of soil would be obtained. But this is bad advice, 

 when the soils in difl'erent parts of the fieli are really unlike. Suppose one 

 part of a field to be clay, and another sandy, as is often the case in this county, 

 and that an averao;e mixture of then is subnitted to analysis, the result you 

 get will apply neither to the one part of the field nor to the other — that is, it 

 will be of little or no value. In selecting a specimen of soil, therefore, one or 

 two pounds should be takm from each of four or five parts of the field where 

 the soil appears nearly alike, those should be well-mixed together and dried in 

 the open air or before the fire. Two separate pounds should then be taken 

 from the whole for the purpose of analysis, or if it is to be sent to a distance 

 should be tied up in clean strong paper, or what is much better, should be en- 

 closed in clean well-corked bottles. 



I. — OF THE PHYSICAL PROPERTIES OF THE SOIL. 



2\ Determination of th-; densily of the soil. — In order to determine the den- 

 sity of the soil, a portion of it must be dried at the temperature of boiling 

 water (212=), till it ceases to lose weight, or upon a piece of white paper in an 

 oven at a heat not great enough to render the paper brown. A common phial 

 or other small bottle perfectly clean and dry may then be taken and filled up 

 to a mark made with a file on the neck, with distilled or pure rain water, and 

 then carefully weighed. Part of the water may then be poured out of the 

 bottle, and 1000 grains of the dry soil introduced in its stead, the bottle must 

 then b3 well shaken to allow the air to escape from the pores of the soil, filled 

 up again with water to the mark on the neck, and again weighed. The weight 

 of the soil, divided by the difference between the weight of the bottle with soil 

 ani water ani th3 sum of the weights of the soil and the bottle of water to- 

 gether, gives the specific gravity. 



Thus, let the botde with water weigh 2000 grains, and with water and soil 

 2000, then- 

 Grains. 



The weight of the bottle with water alone = 2000 



The weight of the dry soil 1000 



Sum, being the weight which the bottle with the soil and water 2 



wmili, kave had co\\\(\. \.\\G scil have been introduced without > 3000 

 displacing any of the water } 



But the weight of the bottle with soil and water was .... 2600 



Difference, being the weight of water taken out to admit 1000 \ .r^r. 

 grains of dry soil \ 



Therefore^ 1000 grains of soil have the same bulk as 400 grains of water, or 

 the soil is 2 J times heavier than water, since 1000 -r 100 = 2-5 its specific 

 gravity. 



3^. Delerminalion of the absolute weight. — The absolute weight of a cubic 

 foot of solid rock is obtained in pounds by multiplying its specific gravity by 

 G3^— the weight in pounds of a cubic foot of water. But soils are porous, and 

 contain more or less air in their interstices according as their particles are more 

 or less fine, or as they contain more or less sand or vegetable matter. Fine 

 sands are heaviest, clays next in order, and peaty soils the lightest. The 

 simplest mode of determining their absolute weight, therefore, is to weigh an 

 exact imperial half pint of the soil in any state of dryness, when tliis weight 



