46 Experimental Philosophy. [Lecture 4. 



different fluids. Thus I have known good house- 

 wives in the country try the body of their mead 

 and other liquors, by observing whether an egg 

 will swim in them, which, we know, will sink in 

 common water. The exact relative weight of 

 fluids may be ascertained by suspending from 

 one end of an accurate balance (such as that fig. 

 17.) either a small globe, or a conical piece of 

 glass. Its weight in water being previously 

 ascertained, which suppose to be two hundred 

 and twelve grains ; if it is immersed in a fluid 

 heavier than water, some weights must be added 

 in the opposite scale ; as for instance, if it is sea 

 water, then ten grains must be added, which 

 will make the relative weight of sea-water to 

 common water as four hundred and twenty-two 

 to four hundred and twelve. If, on the con- 

 trary, it is immersed in brandy, which is less 

 dense, and consequently lighter than water, you 

 will find it necessary to take out of the opposite 

 scale about forty grains, and then the relative 

 weight of brandy to water will be as three hun- 

 dred and seventy-two to four hundred and twelve, 

 or about one-tenth lighter. 



A very convenient instrument is made use of 

 by excisemen, officers of the customs, and all 

 whose business it is to ascertain the density* or 

 strength of liquors. It is called an hydrometer, 

 and is nothing more than a small hollow globe 

 of glass or metal with a stem to it, like the han- 

 dle of a teetotum, but longer, which stem is 



