WHAT SOILS ARE BEST FOR AGRICULTURE? 245 



TEST ON FUNDAMENTAL CONCEPTS 



Make two vertical columns in your workbook. Head one CORRECT 

 and the other INCORRECT. Under the first place the numbers of the state- 

 ments you believe to be correct. Under the second place all the numbers 

 you believe to be incorrect. Your grade right answers X 2-^-. 



I. A rock should always be classified as igneous if it: (1) will 



scratch glass ; (2) is made of crystalline minerals ; (3) is made up 

 of hard layers ; (4) is made of granite ; (5) contains quartz and 

 feldspar. 



II. The following rocks were formed by cooling from a molten 

 state : (6) limestone ; (7) sandstone ; (8) granite ; (9) marble ; 

 (10) fossil-bearing rock. 



III. The land surface of the earth is being leveled by many 

 agents, among them are : (11) ice ; (12) running water ; (13) grav- 

 ity ; (14) the changing phases of the moon; (15) wind. 



IV. The presence of fossils in the rocks: (16) makes it pos- 

 sible to tell the age of the earth; (17) shows when granite was 

 first formed; (18) gives a record of much of the early plant and 

 animal life; (19) shows that there was life on the earth before 

 there was soil; (20) shows that the size of animals on the earth 

 became larger and larger with the passing of time. 



V. Soils which are able to retain moisture are : (21) composed 

 of much coarse gravel ; (22) mixtures of sand and clay with surface 

 freshly rolled; (23) mixtures of sand and clay with the surface 

 layer cultivated; (24) those having the surface covered with 

 thick paper ; (25) those on which commercial fertilizers are used. 



VI. These things contribute to soil-making: (26) heat and 

 cold; (27) solution by water; (28) mechanical action of water; 

 (29) movement of glaciers ; (30) icebergs. 



VII. A good soil for the garden must : (31) contain 90 per cent 

 quartz sand ; (32) have a large variety of metals in it ; (33) contain 

 both moisture and air ; (34) be porous ; (35) be compact like clay. 



VIII. Water may cause erosion by : (36) mechanical grinding 

 action ; (37) evaporation from rivers ; (38) solution aided by carbon 

 dioxide ; (39) hot water in geysers ; (40) wave action. 



THOUGHT QUESTIONS 



1. What agencies have been at work in your locality to produce 

 soil? How have they done their work? 



2. You live in a limestone region and one day find a small cave 

 in a limestone ledge. How would you account for its presence 

 there? 



