478 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



for drain tile. Partly as a result of our work, the general character 

 of tile has been improved, until at the present time most of the large 

 tile manufactured passes the American Society for Testing Materials 

 standards without difficulty, and some of the plants are able to meet 

 specifications requiring an absorption of not more than 8 per cent. 

 The quality of the small tile has been improved somewhat, but there 

 is still need for much experimental work before an entirely satis- 

 factory product will be secured. 



In addition to the laboratory work, a water survey was made 

 through the Red River Valley as far north as the Canadian line, with 

 a view to determining the limits of the area impregnated with dan- 

 gerous alkali salts. 



It is hoped that the final result of the work at this laboratory will 

 be to develop a commercial method of manufacturing drain tile of 

 maximum resistance to alkali salts and determine the area in which 

 it will be unsafe to use concrete tile. 



During the fiscal year 1923 a preliminary survey of the condition 

 of concrete tile in the Southeastern States disclosed deterioration or 

 failure in a number of instances. However, there was a lack of exact 

 information as to the quality of concrete tile used in the tile lines 

 inspected. As a basis for accurate observation there was laid in 

 January, 1923, on a farm near Wilson, N. C, an experimental drain 

 composed of various makes of concrete tile of known quality, some 

 being given protective coatings prior to laying. Each of the tiles laid 

 was tagged for future identification, and the line will be inspected 

 from time to time to determine the condition of the tile and whether 

 the soil constituents have any apparent effect on the tile. 



Run-off investigations were continued throughout the year, the 

 most notable work being done on the Little River drainage district in 

 southeast Missouri, where studies were made on both the large flood 

 way and the smaller tributaries. Rainfall conditions were such that 

 no conclusive data were secured with respect to the flood way. Still, 

 the information obtained was sufficient to show that the coefficient 

 of roughness or the resistance to the free flow of the water in flood 

 ways is larger than is generally believed, and hence a larger coeffi- 

 cient of roughness will have to be used in designing such improve- 

 ments than has been the custom in the past if the estimated carrying 

 capacity is to be obtained. 



A series of flood flows from drainage ditches in the district 

 yielded valuable information with respect to the maximum flow to 

 De expected in ditches furnishing outlet for drained areas of flat 

 bottom land. This information is at present being used in rede- 

 signing the drainage improvements for the Little River district and 

 for a number of districts in northeastern Arkansas. Measurements 

 have also been made of the flood flow from a small hill watershed of 

 150 acres. The results obtained show the maximum rate to be much 

 larger than was generally supposed for the locality. This informa- 

 tion will be of special value in designing road culverts. 



A continuation of the study of the effect of tile drains on the 

 soil, conducted at the Coast Experiment Station in Summerville, 

 S. C., in cooperation with Clemson College, demonstrates that tile 

 drains properly installed are very effective where a good outlet is 

 available. However, there is a considerable area in the Coastal 

 Plain where outlet facilities are not available under present condi- 



