170 THE CULTURE OF FARM CROPS. 



depth may be from 2J to 3 feet; and very rarely more; as 

 the case may require. 18 inches at the surface gives ample 

 room for working in such a ditch; and 6 inches is sufficient 

 for the width at the bottom. In estimating the cost of dig- 

 ging these ditches, the question should be considered, if 4 

 feet ditches at 100 feet apart would not be cheaper than 3 

 feet ditches 60 feet apart : the cost would be less certainly, 

 for the labor of excavating 6 ditches 4 feet deep would be 

 less than making 10 ditches 3 feet deep and the ground 

 covered would be the same in either case. 



The materials, for making the drains in covered ditches 

 are tiles, stones, gravel and wood; and each has its good and 

 bad points. 



Tiles are pipes made of clay burned like brick in kilns. 

 They are made of various diameters from one inch for the 

 short lateral drains up to 6 or 8 inches for the main and 

 outlet drains; and are about 15 inches long. They make 

 the best and most lasting drain, when well made and laid 

 with accuracy. They should be hard burned so as to ring 

 when struck; free from flaws; straight, and smooth at the 

 ends, so that they will make close joints and exclude sand 

 or sediment which might choke them. The ditches should 

 be finished to. an even grade with a narrow scoop made for 

 the purpose, which digs out a hollow the exact size of the 

 tile and thus provides a bed for them in which they lie easi- 

 ly and in a line, and may be placed quickly. To lay the 

 tile the workman stands on the bank of the ditch (all the 

 earth is thrown out on one side only, to give room for this 

 work) and picks up each tile with a red provided with a 

 straight projecting arm at the end, which is put into the tile; 

 and lifting it into the ditch the workman places it in the 

 hollow in line with the one before it, taking care that the 

 joint is made close. The ditch should be wholly finished 

 before the tiles are laid, and the work is begun at the upper 

 part so that there is no possibility of anything being 

 washed into the drains by the flowing water. 



By making the drains in this way there is no risk of 

 making any mistake in any way, either in the grade or in 



