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 brinors 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 wet 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. 



{p) Fill cans i, 2, and 3 to within one-fourtl: inch of 

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

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



[c] 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 

 Xo. I as it is, and carefully pulverize and loosen the 

 soil in Xo. 2 to the depth of two inches, and that in 

 Xo. 3 to a depth of three inches, and cover Xo. 4 with 

 a three -inch mulch of sawdust or straw. 



(<?) 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, Bailey, p. 75- 



