92 Domestic Science 



in the tube so that it floats with a larger portion of 

 its volume immersed. Find the weight of displaced 

 water and the weight of the dry tube and shot as before/ 

 Again compare these weights. 



It will be found that the weight of the solid body 

 is equal to that of the volume of water displaced by 

 it. Put into the form of a general statement this is 

 known as the "Principle of Floating Bodies' 5 , which 

 is as follows : 



The weight of the liquid displaced by a body 

 floating in a liquid is equal to the weight of the body. 



Exercise for Student. 



Devise and carry out an experiment to test the applicability 

 of the Principle of Floating Bodies to a liquid other than water. 



55. Instruments have been devised whereby 

 advantage may be taken of the above principle to 

 determine the specific gravity of a liquid in a very 

 simple manner. They are termed " hydro- 

 meters", and Fig. 28 shows the appearance ,. 000 

 of one of the ordinary forms. B is a long 

 cylindrical bulb of glass. C is a smaller 1 ' 010 

 bulb sealed to the lower end of 5, and i. 020 

 containing a quantity of small leaden shot 

 or some mercury. A is a long stem of 

 narrow bore, in which is a paper scale. 

 This scale is so graduated that the specific 

 gravity of any liquid, in which the hydro- 

 meter will float at such a depth that the 

 level of the liquid is at some point on the 

 stem, may be read directly from the scale. 

 Hydrometer scales usually have a limited 

 range in order to secure a greater degree 

 of accuracy in the measurement obtained 

 and to do away with the great length of 



