[ 3 ] 
In MacConkey’s medium even when the smallest number of organisms 
were present a reaction was obtained with i cc. of the water but not with 
.4 cc. No Indol was formed with 5 cc. of the water. 
With the largest numbers of organisms 8,800 and 1,655 even .in .1 cc 
acid and gas forming organisms were present and Indol and nitrites wen 
formed with 1 cc. of the water. 
On all occasions in 2 cc. acid and gas forming organisms were founc 
but the presence of Indol forming organisms in 5 cc. was not constant. 
The filter bed slopes slightly to a small sump at the southern end int< 
a well 7 feet in diameter and 8 feet deep. From this well, the filter well 
the water is discharged into the main to the service reservoir througl 
a vertical telescopic pipe. The rate of discharge is regulated and the filtei 
head is regulated by the height of this pipe but the inflow to the filter bee 
can also be regulated. The maximum capacity of the main is 60 cub. fee 
per minute which corresponds to a filtration rate of 2.71 gallons per square 
foot per hour and this rate is now constantly maintained from 6 a.m 
to 6 p.m. 
After scraping the main a discharge of 72 cub. feet per minute witl 
a filtration rate of 3.25 gallons per hour was obtained but this has not beer 
maintained. No such rate of filtration should be allow r ed. The objec 
of a filter bed is defeated if water is passed through at such rates. 
The longest run of any filter bed since Mr. Bach has been in charge 
was 3^ months. This was during a dry period and no water could be sparer 
to wash the second filter bed. When this filter was emptied the sand wa: 
discoloured to a depth of 13 in. Only the remaining some \ inch of sane 
appeared to be clean but the stones beneath also appeared to be quite clean 
There is no difficulty whether the filters are clean or dirty in obtaining 
the maximum discharge that the main can take until the loss of filter heat 
is nearly 3 feet. The depth of water on the sand is regulated by a valv< 
in the intake and it is usually kept at rather over 3 feet. 
My first examination of this w r ater was on 29th October after a rur 
of 116 days. At this time the depth of water on the filter was 4.7 in., th< 
filter head 2.8, and the discharge per sq. foot of filter bed 2.05 gallons pe 
hour. 
The second examination on the 15th January was made after a rur 
of 27 days, the depth of w r ater on the filter was 3.5 feet, filter head .30, anc 
the discharge 2.71 gallons per square foot. 
