8 The Profitable Culture of Vegetables. 



has to be evaporated, and the effect of evaporation from any 

 surface is to make it colder. Therefore, well-drained soil is 

 warmer than that which is undrained. The higher tem- 

 perature of drained land has been frequently proved by 

 experiment ; it has been shown to be warmer by as much as 

 six degrees over that of adjoining undrained land, and in 

 addition the temperature of the air immediately above drained 

 land is also several degrees warmer. 



Draining should not be done without careful considera- 

 tion. It is a costly operation when the area to be dealt 

 with is large, and if not properly done may be practically 

 useless. Moreover, there are many soils through which water 

 percolates with sufficient freedom to make pipe-draining un- 

 necessary, and some others of a very open nature where it 

 would be harmful. There is no denying, however, that heavy 

 clays would be improved by draining, always providing that 

 the pipes are put in neither too far apart nor too deep. Many 

 of the drains put in clay land by Government assistance about 

 fifty years ago are far too deep and too wide apart to be of 

 much use. 



On such close-textured tenacious soils, when only shallow 

 cultivation is practised, as in ordinary farming, the custom of 

 laying the land in beds or " stetches," with furrows between 

 connected with cross-furrows, or " water-furrows," is usually 

 found sufficiently effective for all practical purposes, but for 

 garden cultivation on such soil, where deep working is neces- 

 sary, pipe-drains should never be omitted and the cost would 

 soon be amply repaid. 



How to Drain. At various times there has been great 

 difference of opinion as to the direction in which drains 

 should run whether in the direction of the slope or obliquely 

 across it. Experience has proved that it is best to lay them 

 in the direction of the greatest slope. 



Drains are ranged under three classes main-drains, sub- 

 mains, and small drains. The mains are those into which all 

 the other drains deliver their water, and which lead the united 

 flow to the point of outfall ; these should invariably be along 

 the lowest part of the field. Sub-mains should be laid along 



