Fouˊntains

are of 2 sorts, such as dry up in the winter, and such as flow always. Most are of opinion, that the former are prosuced by the rain. Those perpetual springs may be defin’d to be collections of waters running down from the higher to the lower parts of the earth. Out of a great number of such fountains rivers are gathered, which carry the waters into the sea.

Some have imagined, that the perpetual ones are derived from the sea, and that there are subterraneous tubes in the earth through which the sea-water is conveyed to the fountains. But this opinion is liable to these two difficulties, how is it possible for the sea-water to be carried to the tops of the highest mountains, since by all experiments in Hydrostaticks it appears, that the surface of any water contained in any vessel always lies even, so that it is impossible for any one part of the surface to be higher than another; except it be made so by some external force.

2. How it comes to pass that fountain-water is not salt.

Others again dislike this hypothesis, and that for several reasons, and assign rain as the cause of fountains; but if rain were the only cause, whence can it be, that those fountains are never dry in the time of the greatest drought, when there has been no rain for a long time? and therefore others to rain add vapours; which being by the heat of the sun exhaled in vast quantities (as the learned Mr. Edmund Halley has proved) and they being carried over the low-land by the wind to the ridges of mountains, where they presently precipitate, and gliding down by the crannies of stone, and part of the vapour entering into the caverns of the hills, the water thereof gathers as in an alembick in the basons of stone it finds; which being once filled, all the overplus of water runs over by the lowest place and breaking out by the sides of the hills, forms single springs and many of these running down the valleys between the ridges of the hills, and coming to unite, form little rivulets or brooks; and many of these meeting again in one common valley, and gaining the plain ground, being grown less rapid, become rivers; and many of these being united in one common channel, make the largest rivers, as the Thames. the Rhine, the Danube, &c.