Page:Popular Science Monthly Volume 39.djvu/647

Rh it must displace its own weight of the supporting fluid. If, then, a float of invariable weight be immersed in a liquid, the depth to which it sinks will be a measure of the specific gravity of the



liquid. The hydrometer is simply such a float as this. It is made in different forms and styles, according to the use for which it is intended; but in all cases it is essentially a cylinder or bulb of