136 REPORT OF THE CHEMIST OF 



period. Any of you who have measured rainfalls will know that .22 inch of 

 rain is a very respectable shower. This increased water-holding power of 

 tile- drained soils is of great importance, and is not to be overlooked in dis- 

 cussing the effects of tile-draining. The influence of draining is often 

 regarded simply as removing water ; but the secondary influence upon the 

 soil, even if the tile is dry for half the year, is of equal importance with 

 water removal. The conservative influence of underdraining by this 

 increased capacity to hold water when it suddenly comes and is in danger of 

 running off by surface flow, is one of the benefits to be considered. 



Some have attempted to. explain the fact that a tile-drained field will 

 endure drought better than one not drained, by claiming that the air circu- 

 lating through the tiles gives up moisture to the soil, but I think a better 

 explanation is the increased power of the drained soil to hold water in 

 capillary form, and perhaps also from its greater power to draw up water 

 from the deeper soil by capillary action. 



Time of Flow of Field Drains. 



Such observations as I have been able to make on the time of beginning 

 of the flow of water in tile drains after the commencement of a storm con- 

 forms in some degree to the results of experiments already given. Except 

 when the ground is fully saturated with water, as in the thaw of spring, 

 when the water accumulated by the action of frost is rapidly set free, there 

 is a sensible interval of time after the rain begins to fall before the tile-flow 

 sets in. In many rains the tiles do not discharge at all in summer because 

 the increased capacity to hold water enables the soil to absorb all the rain. 

 In the majority of cases when the tiles give a flow it is only after 12 to 24 

 hours — in most cases about 16 — after the storm has begun. By the time 

 the tiles begin to discharge the storm usually begins to break away, and the 

 action of the tile is to prevent flood, instead of augmenting it. Where a 

 flood is caused by excessive rainfall or a " cloud-burst," the flood is caused 

 by the water flowing over the ground and not through it. The great floods 

 that have devastated portions of our country have occurred in regions where 

 tile-draining is almost unknown. Take the floods in West Virginia and 

 around Pittsburg as examples. Some of you may recall the dreadful flood 

 that swept Alleghany City in July, 1874. I visited the scene a few days 

 after and while the marks of the destroyer were not effaced. A sudden and 

 very heavy rain had fallen on the neighboring hills, the water by converging 

 valleys was poured upon the city, the nine foot sewer became obstructed, and 

 the water rose 25 feet in the streets in as many minutes, and the destruction 

 of life and property was awful. Yet in all the track of that storm there 

 were not two miles of tile drains, and if there had. been a hundred miles the 

 flood would not have increased in violence thereby. 



I think the opponents of tile draining will find some difficulty in pointing 

 out regions where tile draining has been extensively carried on, where 

 destructive floods are especially injurious, and to find other localities 

 similarly situated, except in the matter of tile draining, where floods are 

 never known. 



