TILLAGE AND CULTIVATION 69 



by their burrowing. Darwin's book on earthworms 

 contains many interesting facts about them. You 

 will find it very entertaining to watch them and find 

 out how they work. 



SEED-SOWING 



The sowing of seeds was formerly all done by hand. 

 It is still so done in small gardens, and there are cer- 

 tain small seeds which cannot be sown so well in any 

 other way, even in the field, when the sowing is to be 

 done "broadcast," or uniformly all over the surface. 

 This is true of many small flower seeds, and of the 

 meadow grasses. The cereal grains (wheat, rye, barley, 

 oats) were long sown broadcast by hand only, a process 

 which required not a little skill to do it evenly. But 

 for many years they have also been planted in drills by 

 drilling machines, which in a number of states is thought 

 to be best. In others, especially in California, broad- 

 casting of grains is done by means of the " centrifugal" 

 sowing machine. This throws out the seed from a 

 rapidly revolving disk or solid wheel, through the center 

 of which the grain passes, and is thrown out quite 

 uniformly from the rim. This sower is placed on the 

 rear end of a common farm wagon. The wagon is 

 followed by several harrows hitched together so SLS to 

 cover the width of the sowing done. 



Small seeds such as clover and alfalfa are sown by 



