64 
THOMPSON YATES LABORATORIES REPORT 
As in the case of the other beds, the combined area of the bed is one-tenth of 
an acre ; No. 3 bed being 230 square yards in extent, and No. 30 254 yards, with 
a capacity of 230 cubic yards and 254 yards respectively. Owing to the nature of 
the material in 3^, it has been found that the area of the sand bed should be twice 
that of the coke bed. 
These beds commenced working on November 14th, 1899, at the rate of one 
charge per day through No. 3, this being equal to filling 3^ twice. On November 
20th the rate was increased to two fillings of No. 3, or four for No. 30, which was 
continued until the 16th January, 1900, when the rate was reduced to one charge for 
No. 3, owing to the difficulty in getting the water through the sand. As the rate of 
working No. 3*? did not improve, about 2 inches in depth of the surface was removed, 
and on restarting a great improvement was noticed, which, however, only continued 
for 12 or 14 days, the surface becoming gradually clogged up again. The operation 
of removing the surface of the bed has had to be repeated on two occasions, and 
digging over the surface has also been tried, the result in each case being a temporary 
improvement. 
Both beds were opened up for examination at the same time as Nos. 1 and 2. 
No sludge was found in the bottom of No. 3, and no worms were to be seen, but a 
slight covering of sewage matter was on the material of the bed, and large patches of 
a reddish-brown colour, resembling iron-rust, were noticed, especially near the surface. 
No. 3<7 was opened carefully to the bottom, and showed signs of clogging for about 3 
inches from the surface, below which the material appeared as fresh as when put in. 
The following statement shows the capacity of No. 3 bed at the various times 
on which it has been tested by measurement : — 
Date 
Cubic feet 
Gallons 
* November 14th, 1899 
3,5°° 
2 1,870 
1 6th, „ 
3,200 
20,000 
„ 29th, „ 
5.150 
19,690 
December 20th, „ 
2,800 
I 7,500 
January 25th, 1900 
2,700 
16,870 
February 23 rd, ,, 
2,700 
16,870 
March 19th, „ 
2,700 
16,870 
April 23rd, „ 
2,700 
16,870 
The effect produced by the working of the bacteriological beds was most 
marked, not only on the Sewage Farm but on the purity of the River Alt, into which 
* First time of charging, material drv. 
