Ibid., p. 16: "Soil types which constitute the units of soil classification, may be grouped in different ways. As soils are made up of particles of different sizes, they may be grouped according to the relative proportions of the particles of different sizes which they contain. This grouping is known as the soil class and is based on texture. By means of mechanical analyses the particles less than two millimeters in diameter are separated into seven grades, and the various percentage relationships of the different grades determine the class of soil; that is, they determine whether it is sand, sandy loam, loam, clay or some intermediate class. In addition to the fine earth, of which a mechanical analysis is made, many soils contain larger particles, which if small are called 'gravel,' and if of larger size are called 'stones,' so that in the soil classification it is possible to have a gravelly sand, loam, or clay, and likewise stony members of the various classes." The table on the opposite page (ibid., p. 17) will give the reader a better knowledge of soil classification:

Scheme Of Soil Classification

Class

1

Fine gravel 2-1 mm.

2

Coarse sand 1-0.5 mm.

3

Medium sand

0.5-0.25 mm.

4

Fine sand 0.25-0.1 mm.

5

Very fine sand

0.1-0.05 mm.

6

Silt 0.05-0.005 mm.

7

Clay 0.005-0 mm.

Coarse sand

More than 25% of 1 + 2 More than 50% of 1 + 2 + 3

0-15 0-10

Less than 20% of 6 + 7

Medium sand

Less than 25% of 1 + 2 More than 20% of 1 + 2 + 3

0-15 0-10

Less than 20% of 6 + 7

Fine sand

Less than 20% of 1 + 2 + 3

0-15 0-10

Less than 20% of 6 + 7

Sandy loam

More than 20% of 1 + 2 + 3

10-35 5-15

More than 20% and less than 50% of 6 + 7

Fine sandy loam

Less than 20% of 1 + 2 + 3

10-35 5-15

More than 20% and less than 50% of 6 + 7

Loam

15-25

Less than 55% of 6

More than 50% of 6 + 7

Silt loam

More than 55% Less than of 6 25% of 7

Clay loam

25-55 25-35

More than 60% of 6+7

Sandy clay

More Less than than 20% 25% of 6 of 7

Less than 60% of 6 + 7

Silt clay

More than 55% 25-35% of 6 of 7

Clay

More than 35% of 7

More than 60% of 6+7