CRAIGEND PON I is. 



241 





requires to be emptied of sand sometimes as often as once a month 

 in winter. Figs. 164, 165, and 166 are diagrams of the trough 

 and leg, showing leg closed. 



A 4 -inch pipe was laid from the leg, running 

 parallel to the ponds, with a straight-eye opposite 

 the centre of each pond, rising perpendicular, so as 

 to afford a view of the interior of the pipe without 

 interfering with the run of the water. Between the 

 upper and lower 100-feets a connection was laid, and 

 a three-legged trough placed in the line of 4-inch 

 pipes to feed this connection when required. 



The outlets of the 100-feets were made by driv- 

 ing two substantial piles into the end of each pond, 

 and supporting between them a frame carrying a 

 screen-box and screen. The screens were fitted into 

 face-checks and fastened by turn-buttons. Troughs 

 of wood led from the backs of the outlet screen- 

 boxes, carrying off the water. Now that between 

 forty and fifty outlet screens are used at Howie- 

 toun, they are all made interchangeable ; but these 

 screens act well, and some may wish to adopt them 

 for isolated ponds, especially as they do not require 

 any masonry. 



The troughs below the upper and lower ponds 

 were connected with the 4-inch pipe by cross-pipes 

 from the three-legged trough ; and the fall from the 

 upper pond to the lower, and from the lower to the 

 octagon, were sufficient to ensure the temporary 

 supply thus obtainable running the right way, and 

 not flowing back into the pond above. Fig. 167 is i M 

 a plan of the ponds, showing 4-inch supplementary || 

 and G-inch drain-pipes. 



From the above plan the mode of working the FlG- 167 - scale !*r- 

 supply will be readily understood. Should the upper 100-feet 

 require to be drawn, all that is necessary is to open the three- 

 legged troughs at A and B, and stop the water off the pond at A, 



Q 



