EXPERIMENT STATION BULLETINS. 469 



occur small areas underlaid bv nearly impervious strata of clay sub-soil. 

 These isolated areas may be found well up on the sides of slopes and 

 occasionally on the top of the highest portions of fields. Such areas 

 may not contain more than a few square rods and yet so persistently 

 is the water held that the planting of crops is delayed and in some sea- 

 sons actually prevented. One such area amounting to one hundred 

 square rods existed at one time at the highest point of a twenty acre 

 field on the College farm. 



5. Springy places that occur at the foot of slopes, and not infre- 

 quently, well up on the sides of slopes. 



TILE. 



T^'o general kinds of tile are to be found on the market, the so-called 

 common or porous tile and glazed tile. Both of these are manufactured 

 in lengths of twelve inches and in diameters ranging from three inches 

 up to fifteen or more. Occasionally we find tile manufactured in 

 diameters of two inches. The two-inch tile, however, is not much used 

 at this time. 



The glazed tile is doubtless more durable than the porous, but a well 

 burned porous tile made of good material will last for centuries if placed 

 below the frost line. 



Even the best made porous tile is likely to shell if subjected to freez- 

 ing, and both the porous and the glazed tile will crack if the water filling 

 them should freeze. 



Within the past few years the manufacture of cement tile has become 

 somewhat common, and several machines for the manufacture of cement 

 tile are now on the market. There are cases reported of cement tile 

 that has been used for many years, twenty or 'more, and it appears to 

 be as good as it was at the time of making. 



HOW THE WATER ENTERS THE TILE. 



In the case of glazed tile the water can enter the tile only by way 

 of the joints. 



In the case of porous tile, in all but the heavier clay soils, the greater 

 part of the water enters the tile by way of the joints, and perhaps this 

 may be true even in the case of the heavier clays. In a recent experiment 

 it was shown that in the case of porous tile laid in lines four rods apart 

 the rate of flow through the walls of six-inch tile was two tons per acre 

 in thirty hours, while in the case of four-inch tile laid in the same way 

 the rate was 1.55 tons per acre in thirty hours. In these cases the tile 

 was very hard and of the porous kind. With four-inch common, more 

 porous tile laid in the same manner as above, the rate of flow was 1.66 

 tons per acre in thirty hours. In the case of four-inch cement tile laid 

 in the same manner and under the same conditions the rate of flow 

 through the walls was twelve hundred and twenty-four tons per acre in 

 thirty hours. 



TILE SYSTEMS. 



In the draining of a piece of land there are several things that should 

 be carefully considered. It may be that a single line of tile will be 

 sufiicieut to remove all surplus water from the area to be drained. This 



