CI I 



of wliicli tile gate may be raised or lowered. '^C, (7, C" 

 represent crib- work, tilled with stones, and sustaining 

 in position the screens 5, s and 0. 0, which are arranged 



to slide in their respective grooves, similarly to those 

 already described. 



A liume or trunk of somewhat simpler and cheaper 

 design : which may be constructed by holloAving out 

 one side of a stout log, for nearly its entire length, 

 and covering the groove thus formed with pieces of thick 

 plank, is also figured : the bark should l)e allowed to 

 remain undisturbed, where practicable, for the sake of 

 the protection which it affords to the wood. The gen- 

 eral arrangement of the flume and its valves is so plainly 

 indicated in the diagram as to render further descrip- 

 tion unnecessary ; it will only be remarked, therefore, 

 that as the valves do not w^ork automatically, such a 

 "plug-trunk" — as it is called — would appear to be better 

 adapted for ponds located in other than tidal regions. 



