lake. Water. On the motion of a sudden rush made by a river over its dry bed. The course of the water delivered by the overflowing lake to the dry river is so much slower or swifter as that river is wider or narrower, or flatter or deeper in one place than in another. By what has been set forth, the flux and reflux of the sea that enters from the Ocean into the Mediterranean, and of the rivers that joust with it, raise their waters so much more or less as that sea is more or less narrow. On the siphon of quicksilver for making fire.

S n m t f. Because the more the water diminishes in the vessel, the more its surface sinks; and the more the surface of the water sinks, the more slowly its siphon pours. But if the siphon were to descend together with the surface of the water that sustains it, without doubt the motion of the water pouring through the siphon would always be equal in itself. Therefore, to achieve this equality, we shall make the vessel n, a vessel set upon the bath of quicksilver m; this vessel n is a boat that sustains the siphon, through whose bottom the siphon passes from the air into the quicksilver; and this quicksilver goes pouring through such siphon n S t into the vessel f; and as much as the surface of that quicksilver descends, so much does the boat descend that rests upon it together with the siphon. Which is a very fine wire of quickened copper, and it falls into the vessel; and this, when it acquires the due weight, falls, making fire by the blow.

From the skin of the bath to the end that the siphon has outside, let the drop be imperceptible.