88 TALKS ABOUT THE SOIL. 



it, the better will they grow. This was learned long 

 ago ; and various things have been used to scratch the 

 soil, break up the lumps, and make it fine and soft. 

 No doubt the first thing used was a branch of a tree 

 dragged over the ploughed land. Such things are still 

 used ; as when a farmer, wishing to smooth over a 

 rough field, cuts down half a dozen small birch-trees, 

 and fastens them by the ends to a wooden cross-bar 

 dragged over the ground by a horse. From some 

 such tool came the modern harrow. This horse-tool 

 is now made in many shapes, the most common being 

 a wooden triangle armed with iron teeth. In place 

 of teeth, metal disks and shares of various shapes, 

 and even chains, are sometimes used ; and, when 

 dragged over a ploughed field, soon make the soil 

 smooth, soft, and loose, ready for the tender roots of 

 young plants. On heavy clay lands, where the plough 

 is apt to leave the soil in hard lumps, another tool 

 called a clod-crusher is used in place of a harrow. 



Beside these various forms of ploughs, harrows, cul- 

 tivators, and hoes, there are also the spade and the 

 garden-rake. The spade is a tillage tool for inverting 

 and breaking up the soil, and the iron rake is for 

 stirring the top of the soil about young plants. For 

 small work, there are also trowels and small hand- 

 rakes. 



XVin. EXPERIMENTS IN TILLAGE. Not many 

 years ago the farmers in a certain part of Ohio found, 

 as many American farmers had found before, that their 

 fields produced less and less wheat year after year. It 



