116 Surface and Underground 



easily be obviated by making the grating longer, with the 

 bars lying in the direction of the stream, the force of which 

 would keep the grating clear. 



This culvert, from its size and inclination, is sufficient to 

 carry off the water of the heaviest thunderstorm recorded. 



The channel marked D, at the south end of King-street, 

 drains 53 acres, and the channel marked E, at the south end 

 of Russell-street, 27| acres ; giving a total area of 957'05 

 acres drained by the five outlets A, B, C, D, and E. 



These channels have also another source of supply beside 

 the rains, namely, the waste water or ordinary sewage from 

 houses, cellars, shops, yards, baths, wash-houses, dye-houses, 

 water engines, manufactories, urinals, the overflow of cess- 

 pools, stables, fountains, street-watering, &c. 



To determine the amount of water flowing in the street 

 channels from these sources, I have made a series of experi- 

 ments at the outlets B and E, the respective areas drained 

 by them being 248 2 and 27 "5 acres. 



The first experiments were made at the outlet E, near the 

 Duke of Wellington Hotel, Russell-street and Flinders-street, 

 and the results, from actual measurement, gave a mean result 

 of 4 3 3 gallons per minute.* 



The next experiments were made at the mouth of the 

 stone culvert crossing Flinders-street at the end of Swanston- 

 street, and the mean results of the various measurements 

 gave 39 7 J gallons per minute. 



The measurements in both cases were made at periods 

 when no rain had fallen within 48 hours ; the streets and 

 ground being dry, and the channels uninfluenced by rain. 



The discharge at B and E gave respectively 1561 and 

 1'574 gallons per acre per minute ; quantities approximating 

 so closely to each other that it was only after repeatedly 

 checking the measurements and calculations that I was 

 satisfied of their being correct. 



The quantity of sewage or waste water discharged at the 

 outlets B and E, according to the experiments, is at the rate 

 of 203,670,000 and 22,758,480 gallons per annum, and by 

 applying the mean of the two measurements to the areas 

 drained by the other outlets, we have in Table H the total 

 quantity of rain and sewage discharged by each outlet per 

 annum. 



* The water was measured in a rectangular cistern, accurately made 

 measuring 72 x 19 x 5 9-16ths = 4005 cubit inches, which was filled in 20 

 seconds. 



