BY HARDOLPH WASTENEYS. lll 
In spite of the comparatively large amount of organic 
matter which it contains this water is not by any means 
an ‘acid’ water, except by virtue of its “ Free Carbonic 
Acid,” that is to say it contains no acidity due to “ organic ” 
acids. 
In no case would any of the samples obtained from the 
lagoon have been considered suitable for a town supply if 
only on account of the amount of organic matter indicated 
by the figures quoted. 
Having thus briefly reviewed the Physical, Biological 
and Chemical conditions obtaining in this lagoon, I now come 
to the second portion of my paper, viz., the description of 
methods of rendering this water fit for a town supply. 
Before commencing on this subject I would like to make 
one more disclaimer. I have had no opportunity of testing 
the processes about to be described on anything like a large 
scale, the results having been obtained on small filters, the 
largest being 76 square feet in area, and yielding nearly 
5,000 gallons of filtrate per 24 hours. Nevertheless, the 
greatest care has been taken in every case to imitate as closely 
as possible the conditions which would exist were the filter 
an acre or more in area, and I am confident that the results 
obtained on this experimental scale closely approximate 
to those which would be obtained on the larger scale required 
for a town supply. 
It may be well at this stage to consider briefly the 
various methods in use for securing a pure supply of water 
from a source of this nature. 
First there is the method sometimes adopted of cleaning 
the watershed and also the lagoon which contains the water 
collected from it. This is a most desireable proceeding, though 
there exists some doubt as to the permanency of the benefits 
to be derived from cleansing the bottoms of such lakes, but 
time does not permit of going into the question in detail here. 
With smaller lakes it is sometimes the practice in warm 
climates to roof them over entirely, thus preventing the 
growth of the various forms of microscopic life which are 
responsible for a large portion of the obnoxious odours and 
tastes in the water. Water stored in this fashion, collected 
of course from a clean watershed, but which before roofing 
