Lampas, or Descriptions of Mechanical Improvements of Lamps and Waterpoises

The third method, then, is:

Take any round vessel whose inner concavity and outer convexity are precisely shaped original: "turned," likely on a lathe relative to an axis. Suspend that vessel upon two small pivots (ensuring they are strong enough to support the vessel when filled with oil, etc.) fastened at the poles the endpoints of that axis. Leave or cut open about a sixth of the side (more or less as you prefer) so that items can be placed into or removed from the cavity hollow interior of the vessel.

Then, balance original: "poise" the vessel exactly on those center points so that no side is heavier than the other. Next, fit into it a float made of brass, silver, tin, lead, etc. This float should be curved original: "convex" on the underside to perfectly match the cavity of the vessel. The upper side of the float can be flat, curved, or any other convenient shape; it does not matter much. Make this float as heavy as possible at the bottom and as light as possible at the top, but ensure it is of a weight that allows it to float well upon the surface of the oil.

Fasten one end of this float with a wire or string so that that specific end always touches the point on the inside of the vessel where it is tied, while the rest of the float can rotate and follow the sinking level of the oil. At the end near the fastening point, insert a pipe to hold the wick; this pipe should not allow oil to leak into the cavity of the hollow float.

Once this is done, fill the vessel as full as is practical with oil and light the wick. You will find that as the fire consumes the oil, the vessel will rotate on its poles pivots and keep the surface original: "superficies" of the oil at the same distance from the flame as when you started, until all the oil is used up.

This will be easier to understand with a diagram and explanation, which is provided below in Figure 5.

A C B B represents a hollow vessel, the cavity of which is very precisely shaped turned on an axis with poles at point P. The space between A and B on the side is left open to the cavity. This vessel is suspended