OBSERVATIONS OF CHANGE OF TEMPERATURE 39 



which mix together so completely that they readily come to 

 the same temperature throughout. The errors, due to changes in 

 other bodies, must, however, always be taken into account. 



Various methods of raising different kinds of matter to 

 the same temperature are possible. It is convenient to 

 place them in thin glass vessels inside a larger vessel of hot or 

 boiling water until a thermometer indicates the same tempera- 

 ture. 



32. Equal Quantities of Ice Melted during Equal Tem- 

 perature-changes in Equal Quantities of the same Kind of 

 Matter. 1. Place equal quantities of ice in equal quantities 

 of water at the same temperature, and observe in each case that 

 the water is at the same, though lower, temperature, after the 

 ice is melted. 



2. Observe that the quantity of ice melted in an ice calori- 

 meter varies directly with the quantity of matter used, pro- 

 vided the bodies inserted are of the same temperature and of 

 the same kind of matter. 



3. Observe that equal quantities of different kinds of 

 matter at the same temperature melt different quantities of ice, 

 although they have meanwhile undergone the same changes of 

 temperature. Use mercury and water. 



The above exercises show that the same physical change 

 that is, the change of a given quantity of ice to water is 

 Accompanied by an external change of temperature, which 

 varies in different kinds of matter, but bears a simple relation 

 to the quantity of matter undergoing it. The same change, 

 of temperature in equal quantities of the same kind of matter 

 is accompanied by equal changes, whether of temperature or 

 of another class, in equal quantities of other bodies, but the 

 same temperature -changes in equal quantities of different 

 kinds of matter are not equivalent. They are not reciprocal 

 with equal changes in other bodies. 



The change from ice to water is not a change of tempera- 

 ture. The temperature remains the same, although neigh- 

 bouring bodies simultaneously undergo a considerable thermal 

 change which may be shown to be, for the same quantity of 

 ice, constant in magnitude, 



