re also divided into those of fresh water, and those of salt. Dr Halley is of opinion, that all great perennial lakes are saline, either in a greater or less degree; and that this saltness increases with time; and on this foundation he proposes a method for determining the age of the world.

Large lakes answer the most valuable purposes in the northern regions, the warm vapours that arise from them moderating the pinching cold of those climates; and what is still a greater advantage, when they are placed in warmer climates at a great distance from the sea, the exhalations raised from them by the sun cause the countries that border upon them to be refreshed with frequent showers, and consequently prevent their being barren deserts.