72 AGRICULTURE. 



ers* (Fig. 22) are usually better than rollers, 

 since they grind the clods instead of pushing 

 them down into the soil, and make a smooth sur- 

 face for seed-bed. Rolling after planting may 

 aid the germination of the seeds in dry weather, 

 as it brings the moisture within their reach; 

 especially is it beneficial in the case of fine 

 seeds. Rolling compacts the soil (hence it 

 benefits a light, open soil), but should not be 

 practiced upon a heavy or ivet soil. 



EXPERIMENT 14. (#) Take four gallon-cans, or paint 

 buckets, label them i, 2. 3, 4. Make several holes in 

 the bottom of each, and put a layer of coarse stones, or 

 pieces of broken pottery, in the bottom. 



(l>) Fill cans i, 2, and 3 to within one-fourth inch of 

 the top with mellow soil, and can 4 to within three inches 

 of the top. Firm the soil well in each can. 



(f) Stand all of them in water until the surface soil 

 becomes moistened. How does the surface become 

 moist? In field conditions, how would this supply of 

 moisture be obtained ? 



(</) Take them out of the water and allow them to 

 stand until the surface is dry enough to work. Leave 

 No. i as it is, and carefully pulverize and loosen the 

 soil in No. 2 to the depth of two inches, and that in 

 No. 3 to a depth of three inches, and cover No. 4 with 

 a three -inch mulch of sawdust or straw. 



(e) Weigh each can separately, and record the weights. 



(/) Place all under similar conditions if possible, in 

 an open window, or where the air will pass over them 

 freely. 



* Fertility of the Soil, Roberts, p. 103, and Principles of Agri- 

 culture-, Hailey, p. 75. 



