292 SEWAGE AND ITS PURIFICATION 



valve which opens and closes in such a way that as the pressure 

 at the orifice of the jet slightly increases, the filter bed is covered 

 from the centre of each jet gradually until the maximum radius 

 of 4 ft. 6 in. is obtained, and then the pressure falls off and the jet 

 gradually dies away. The pipe lengths are fitted with cleaning 

 caps, and an emptying pipe for use in frosty weather (see 

 Fig. 38). 



{d) Ham and Baker's Nozzle Distributor and its application 

 at Birmingham are shown in Figs. 39 and 40. Their Revolving 

 Sprinkler is represented later in Fig. 50. 



(e) Columbus, Ohio. Hering and Fuller kindly give me the 

 following details of the proposed arrangements for the 10 acres 



[Fig. 40. — Ham and Baker's Nozzle as used at Birmingham. 



of filter beds. Each bed, 2 J acres in area, is estimated to yield 

 two million gallons per acre per 24 hrs., dealing with septic tank 

 effluent only, with an average period of flow through the tank 

 of about 8J hours. The rows of sprinklers are to be worked 

 from 6-in. underground mains, the nozzles being 15 ft. 4 ins. 

 and the mains 13 ft. 3 ins. apart. Each nozzle will be mounted 

 on a 3-in. cast-iron rising branch from the 6-in. supply main. 

 After extended experiments the type of nozzle chosen was of 

 brass, having a single orifice I'V in. diam. with rounded edges, 

 above which an inverted cone is held by two thin arms, the 

 axes of the cone and orifice coinciding. The jet of liquid 

 impinges against the cone and is transformed into a thin sheet 

 which spreads out radially and then breaks into a mass of drops, 

 which fall on the area included between two concentric circles. 

 For each nozzle to discharge I3'5 gals, per minute, a head of 

 5 ft. is required. In operating it is intended to vary the head 



