450
12, With the exception of the samples collected in January, February, April and May the specimens were found to be clear when observed in a column 24 inches long. It is, however, only right to mention that, in the early part of the year, the filter beds could scarcely be expected to show the best results. They had not been in working order many days when the first samples were collected; and, until after the first considerable fall of rain in May, had not been fully tested with an abundant supply of water. Moreover, owing to the long drought, water at the lowest levels of the reservoir containing a large amount of suspended matter, had to be utilized.
13. This consideration, however, only affected the appearance of the water during four months of the year and then only to a slight extent. From June onwards the samples left but little to be desired in this respect.
14. Throughout the year there was a complete absence of free ammonia, and on no occasion did the albuminoid ammonia and oxygen absorbed reach higher figures than .0042 and .031 respectively.
15. The results given in columns ii to vii, whether viewed collectively or singly, are eminently satisfactory. At any period of the year the Pokfulam water as supplied to the consumer may be classed as a water of great organic purity.
16. In the following table will be found the results of the analyses of filtered water from the Taitam service. The samples were collected at a fountain at the lower end of the Peak road :---
Table B.
ANALYSIS OF TAITAM WATER.
i.
Results expressed in Grains per Imperial Gallon (1 in 70,000).
ii.
iii.
iv.
vi.
vii.
1891.
Appearance in 24-in. Tube,
Total solid matter dried
Chlorine.
Hardness.
at
Saline Ammonia.
Albuminoid Oxygen Ammonia. absorbed.
212° F.
January, February,
P. y. ; C.
4.2
.6
; s. t.
4.1
.6
March,
"2
; C.
3.9
.6
April,
وو
; s. t.
5.3
May,
J.; t.
8.7
.6
June,
P. y. ; s. m.
4.5
July,
*
; C.
3.9
August,
2.6
.6
39
39
September,
3.9
.6
October,
"
; s. m.
4.3
November, December,
"
19
3.5
.6
19
; c.
3.6
.6
OGO7O769908 Co
1.8
None
.0042
.010
1.8
.0028
.025
2.1
"
.0028
.008
.7
1.9
.0028
.019
J
1.7
.0007
.0112
.041
1.7
None
None
.002
1,6
ور
.0042
.017
1.2
None
.002
1.2
"
.005
"5
1.8
.0028
"J
.006
1.6
None
.004
>>
1.6
כל
.004
11 months' mean excluding May..
4.0
.6
1.7
.0018
.009
Abbreviations:-Vide foot note to Table 4.
17. The only unsatisfactory feature in this table is the abnormal character of the water recorded in May. In this instance the water was collected a few days after a very heavy fall of rain. In the last week of April the Taitam supply was nearly exhausted, and, with the first downpour, a large quantity of earthy matter was washed down the exposed slopes of the reservoir which had the effect of making the water exceedingly turbid. On the 19th, the day on which the May samples were collected, the water contained, by the time it reached the beds, fully 8 grains per gallon of suspended matter. In paragraph 5 of his Annual Report for 1891, the Resident Engineer gives 800 gallons per square yard per diem as the maximum rate of filtration. The removal of this quantity of suspended matter therefore involved the deposition of about one pound of clayey matter on each square yard of the filtering medium or one ton on the surface of the 6 beds during the first twenty-four hours. This had the effect of rapidly reducing the rate of filtration, and in a few days only an insignificant quantity of water was able to pass through. In this emergency the beds were overtaxed and a considerable quantity of unfiltered water had to be run into the service tank for several hours in order to keep up the supply pending the cleansing of the filters. If, however, excluding the figures recorded under May, a mean be calculated on the results of the analyses in the remaining 11 months, it will be found that the filtration of the Taitam water has been during that period as efficiently conducted as that from the Pokfulam area. For practical purposes the means may be said to correspond.