110 



SEASON 1874-75. 



times renewed, the screen has never once failed me : it has 

 always taken in the last drop of water in dry weather ; it has 

 never once clogged in floods ; it has never frozen, though some 

 winters have been severe ; and, lastly, it has required no attention 

 except new zinc at most once a year, no daily inspection, no 

 hourly cleaning, as I have too often known hakes or gratings 

 require in wet weather. 



Fro. 52 scale -fa. 



A short spout from the leaf-screen (Fig. 52) conveys the water 

 to a filter. This spout was cut on one side so as to give an over- 

 flow, and covered with perforated zinc No. 9 to guard against any 

 leaves or dirt being washed in off the top of the zinc of the leaf- 

 screen. Both this spout and the end of the leaf-screen are sup 

 ported over the old bed of the stream, so any debris washed oft 

 them is freely carried away. At the lower end of the spout a 

 sluice is fixed to regulate the supply to the filter ; this is set 

 a,gainst a head of water equal to the depth of the interior of the 

 spout at the cut, so that no more than the maximum supply 

 required can pass. All over this of course flows through the cut in 

 the side of the spout, and the flow into the filter remains constant. 



It is unsafe to attempt to regulate water by a sluice until it- 

 has been passed through a leaf-screen ; in fact, with burn- water it 

 is impossible, as sooner or later the sluice will clog. Water may 

 be passed over an overflow sluice with safety, but it cannot be 

 passed under a sluice under the pressure of a head of water, 

 however small, before it has been screened, without the certainty 

 of its stopping. If this is forgotten the penalty will be loss, perhaps 

 total loss. 



