“Fluids,” says he, “are different in weight, as may be proved by the specific gravity of oil and honey compared with that of pure water;” and the given proportion agrees almost with that found by modern experiments. “This,” adds he, “may be discovered by an instrument,” which he thus describes:--“It consists of a thin metallic cylinder made of silver or copper, about as large as the joint of a reed between two knots, to the end of which is added a cone. This cone makes the lower end so heavy, that the instrument, without sinking or floating on the surface, remains suspended perpendicularly in the water. Lengthwise, upon the cylinder, is drawn a line, which is divided by cross lines into as many parts as are equal to the weight of the instrument in _scripla_. If placed in light fluids, more of the divisions will be covered than when put into heavy fluids; or it sinks deeper into those which are light than into those which are heavy. This difference of gravity may be found also,” continues he, “by filling vessels of equal size with the fluids and weighing them; for the heavier must then weigh most; but when one takes an equal weight of two fluids, the lighter will occupy more space than the heavier. If twenty-one divisions of the instrument are covered in water, and twenty-four in oil, and if one take twenty-four _scripla_ of water, twenty-one _scripla_ of oil only can be contained in the space occupied by the water.” Such is the manner in which Professor Klugel has conjectured the meaning of the author from hydrostatic principles; though neither he nor Wernsdorf has ventured to give a literal translation of the words which ought to convey this explanation. But however obscure they may be, it evidently appears that they allude to a hydrometer.