M(1)69
# MINERALOGICAL,
The 310 samples of metals and ores examined during the year comprised the following:-
## Metals.
1925. 1924. Alloys 44 0 Antimony 1 2 Bismuth 22 57 Copper 1 1 Silver 1 1.4 Tin... 208 151 Wolfram 42 33 Zinc. 3 Total....... 322 245.4 1925. 1924. Antimony 0 0 Bauxite... 1 0 Iron 23 9 Manganese ... Nickel + Tin... 151 90 Wolfram 33 75 Total....... 220 151## WATER SUPPLIES..
The examination of the Colony's water supplies is a branch of the work which has greatly increased during the past ten years. The number of samples examined in 1915 was 36 while those analysed during the past year amounted to 595.
This figure includes 244 samples of unfiltered and filtered water taken at the various filter beds and 344 samples of tap water taken by members of the Laboratory staff from taps in houses and offices in many parts of the City and elsewhere.
In addition to the usual physical and chemical tests the electrical conductivity test has been introduced during the year and is now used on all samples..
In March, a special investigation of the Aberdeen water supply was made to ascertain the cause of the nitrate-reduction which was found to be going on in the water. This was found to be due to a harmless Crenothrix growth.
In May an investigation was made into the cause of a brown deposit on the gravel in the pre-filters at the Eastern filter beds. This deposit was formed after chlorination and was found to be due to the decomposition of a Crenothrix growth containing both iron and manganese by the free chlorine.
The increase in water examination work which has been and still is taking place, has fully justified the provision of the special room for water analysis completed in 1924.