OPERATIONS OF TILLAGE. 149 



of unequal diameter, that with the larger cylinder will 

 be more efficacious than that with the smaller cylinder, 

 because a greater weight can be brought, by the exertion 

 of the same force, to act upon the ground. 



Fig. 36. 



The uses and advantages of the roller are many and 

 important. It is particularly serviceable in the seeding 

 process, to break down the clods, pulverize and smooth 

 the surface, and to press the earth to the smaller seeds, 

 which otherwise often fail to germinate for lack of moisture. 

 This is particularly the case with oats, barley, and grass- 

 seeds. In autumn, the roller is sometimes passed over 

 winter grain, with the view of counteracting the injurious 

 effects of frost the following winter. In spring, it is ad- 

 vantageously drawn over winter grain, as soon as the 

 ground is so solid and dry as to bear the tread of the cat- 

 tle without poaching it. It renders light ground more 

 compact, presses the soil to the roots of the grain, and 

 thus promotes its growth ; and upon all soils it closes 

 the innumerable cracks and fissures which abound upon 

 the occurrence of dry weather in spring, occasioned by 

 the abstraction of moisture and the consequent contraction 

 of the soil, — and, by partially burying the crown, causes 

 grain to tiller better, that is, to send up more seed-stocks. 

 13* 



