xiv Illustrations 



FAGS 



Anopheles in a Mosquito-Bar Exposed to 

 Air Currents at Night . . . -114 



Cracks in a Hydraulic Fill . . .120 



Longitudinal Section and Cross-Section of 

 AN Intercepting Tile Drain . . . 131 



Detail of Outlet of a Tile Drain . .135 



Plan and Side View of a Junction of Tile 

 Lines 136 



Concrete Lining of a Ditch of Small Cross- 

 Section 138 



Reinforced Thin Concrete Lining of a 

 Roadside Ditch, and Support of the 

 Sliding Toe of a Hill with Condemned 

 Cross-Ties 138 



Plan and Cross-Section of a Key- Wall and 

 Position of Weep-Holes . . -139 



Concrete Ditch Lining .... 140 



Concrete Lined Ditch at Balboa . . 140 



Key-Walls to Prevent Water Leaving 

 Lined Ditches . . . . .140 



Branch Ditches . . . . . .141 



142 



Junction of Concrete Ditches, Showing 

 Splash- Wall 



Concrete Lining for the Bottom of a Small 

 Ditch 142 



