FIFTH ANNUAL YEAR BOOK — PART VI. 527 



other way, it is advisable to sink a well three or four feet in diameter through 

 the clay to the stratum of gravel. The well will aflEord an adequate outlet 

 for the tile system and in this way the basin in which the muck soil is found 

 is adequately drained and rendered productive. When this plan is adopted, 

 care must be taken to lay the tile in such a way that the water can readily 

 enter, but that mud will not be carried into the well. 



Experiments apparently show that the permanent water level in these 

 muck soils should be maintained at least forty-two inches below the lowest 

 part of the muck bed. 



Numerous peat beds are found in the Wisconsin drift area of Iowa. This 

 type of soil, free from silt and fibrous in texture is often found in strata 

 three feet or more in depth. Peat of this depth is difficult to tile for the 

 reason that when peat beds are drained they shrink greatly in volume. The 

 result is that in a few years' time the surface is lowered to quite an extent 

 and the tile are left too near the surface. King makes the following state- 

 ment regarding the drainage of peat: 



"It is usually better to drain with open ditches, placing them where 

 ultimately they may be deepened and converted into under-drains. The 

 surface ditching will dry out the marsh to a considerable extent, and per- 

 mit the needed decay and shrinkage of the peat to take place, although 

 several years may be required for this." 



We must conclude that there is a great lack of -reliable data regarding 

 the drainage of many types of soil. We trust that during the coming year 

 many farmers and engineers will carefully study the relation of the soil to 

 underdrainage and that in future years the results of these investigations 

 may be published to aid in the advancement of drainage improvements. 



NOTES AND TABLES ON DRAINAGE ENGINEERING. 



Assistant Professor L. E. Ashbaugh, Department of Civil Engineerings 

 Iowa State College. 



The weather and soil conditions of the past two years have caused the 

 people of Iowa to realize the need of drainage. Iowa land is now too 

 valuable to be permitted to remain a waste on this account. The question 

 then arises as to the method of securing the desired results. 



In the past a considerable part of the drainage work attempted has 

 proven unsatisfactory because done without the services of a competent 

 drainage engineer. The grades and sizes of drains has usually been merely 

 guessed at. To help remedy this the following tables and notes of informa- 

 tion have been prepared by the Civil Engineering Department of the Iowa 

 State College: 



