SIZE OF LATERAL DRAINS. I47 



increase the size of the main tile, by figuring to carry 

 J inch of water in twenty-four hours, thus doubling the 

 size that would otherwise be required. 



In the consideration of questions relating to the size 

 of drains, and provision for surface overflow, it will be 

 seen that there is room for the exercise of knowledge 

 and good judgment, and it may be added for the in- 

 formation of those who are sceptical regarding the 

 value of the care thus far urged, that it is necessary if it 

 is expected to realize the best results from the drainage 

 work. 



Selection of Tile, 



The tile selected should be well burned, and hard 

 enough to give a clear ring when struck. They should 

 be uniform in size, so that each size can be laid in a 

 smooth and continuous line without ragged projections 

 on the inside. The approved form is the round tile I 

 foot long. Sizes larger than lo-inch are better if made 

 24 inches long. There are many different qualities of 

 tile, owing to the variety of clays that are worked for 

 this purpose. The two general classes are known as 

 *' red tile" and *' vitrified tile.'' The first are made 

 of common clay and are very generally used for farm 

 work. They are not always red in color, but are not 

 vitrified and come under the general class. There are 

 comparatively few of these that will endure alternate 

 freezing and thawing such as the outlet of main drains 

 is subject to, so that for such exposed places vitrified 

 tile should be substituted. Many of them will not en- 

 dure the exposure of the winter, when placed in piles 

 on cultivated land, without scaling or chipping off* 



