OBJECTS.] INTRODUCTORY. 51 



33. The taking away of Heat from Steam 

 causes the Steam to change into Hot Water. 



Now take a cold spoon, or a cold plate, and hold it 

 against the jet of steam, for a moment or two. 

 When you take it away, you will find that it is quite wet, 

 being covered with drops of warm water, and, more- 

 over, the cold spoon, or plate, has become warm. 

 And if you fit a long cold metal pipe to the nozzle 

 of the tea-kettle, you will find that no steam at all 

 issues from the end of the pipe, but only water, while 

 the pipe becomes warmed. 



Thus the heat passes from the fire into the sauce- 

 pan, or kettle, and thence to the water which they 

 contain ; the water gets hotter and hotter, and, when 

 it has taken in a certain quantity of heat, it becomes 

 steam, or vapour of water. When the steam comes 

 against the cold plate, or passes through the cold 

 pipe, it gives up the heat it has taken in to the plate, 

 or the metal of the pipe. They carry off the heat 

 which kept the water in the condition of a vapour, 

 and so it passes bacK into the condition of liquid. 



Thus steam and water are two conditions of the 

 same thing, water; they are effects of the quantity 

 of heat which the water has taken in. 



34. When Water is changed into Steam, 

 its Volume becomes about 1,700 times greater 

 than it was at first. 



If you could measure and weigh the water in your 

 kettle to begin with, and then measure and weigh all 

 the steam into which the heat of the fire changes it, 

 you would find that the bulk of the steam was nearly 

 1,700 times as great as the bulk of the water, though 



