A considerable dose of chlorine was present in a sample taken from the bottom. This was the more remarkable as the pipe discharged the well-water at the top of the tank. The denser saline water sank to the bottom, without mixing appreciably with the lighter rain-water. I see no reason, therefore, to anticipate any inconvenience from salt, especially as the water will always be drawn for use from the upper strata by means of suitably arranged valves at different levels.
It is just possible that marine organisms living in the sand may be killed by the fresh water and contaminate it. Such a case occurred in the case of a filter-bed (not a reservoir) in Grenada. The sand for this was coral sand taken from the shore near to low water mark. Apparently it was clean, but it must have contained living coral insects. These were killed by the fresh water and imparted to the filtrate a most offensive taste and smell. The sand was removed and replaced by other coral sand collected from above high-water mark, when the inconvenience ceased.
The conditions in this case were quite different from those which will obtain in the present instance. The water actually passed through the sand, carrying with it the offensive products of decomposition. Here, again, drawing from near the surface will prevent any inconvenience.
It was often found in Malta that the lower strata of water in the house-tanks showed unmistakable signs of sewage-contamination (free and albumenoid ammonia), while surface water was perfectly good. In such cases, however, there was actual infiltration of sewage from some leaky house-sewer. This was so often the case that the use of pumps, though prescribed by law, was abandoned, as they drew