When two rivers meet or a river flows down into the sea, at the point of confluence, in spite of coming together, the two waters remain separate and a line of demarcation can be seen for quite a distance. The writer of these words has witnessed this scene at the meeting place of the rivers Ganges and Yamuna at Allahabad. This happens under the natural law which in the present age is known as ‘surface tension’. Similarly, at the sea coast when the tides are rising the salt sea water rides over the coastal river’s fresh water. But the surface tension keeps the two waters separate, and when the tide goes out, the saltish water withdraws from above (without affecting the water below), and the fresh water below maintains its natural character. Due to this surface tension law, it has been possible to find reservoirs of fresh water in the very midst of salt sea waters to meet the needs of voyagers.