44 LATENT HEAT — STEAM. 



of water, it will not become warm so soon; the ice 

 melts, but the water thus formed will remain ice-cold 

 until the whole of the ice is melted, because all the 

 heat supplied to it by the fire is absorbed or combined 

 with the ice in melting; and therefore as the heat so 

 absorbed does not make the melting ice any warmer, 

 it is called latent. When all the ice is melted, the 

 water will begin to get warm. 



49. In the same way heat is absorbed, or rendered 

 latent, when water is converted into steam. If a 

 kettle full of cold water is placed on the fire it rapidly 

 beomes hot until it begins to boil ; but as soon as that 

 is the case it remains constant at the same tempera- 

 ture. The fire of course continues to give out as 

 much heat as it did before, but the water does not 

 become any hotter; the only change is that a small 

 portion of it is converted into steam, and this steam 

 is not apparently any hotter than the boiling water 

 itself was. All the heat of the fire, therefore, be- 

 comes latent, and is combined withr the water in thus 

 changing it into steam. 



50. When steam is condensed, all that heat which 

 became latent during its formation, is given out again 

 in the free and sensible form. This fact is well shown 

 in all stills, in which we see how large a quantity of 

 cold water is necessary to cool and condense a com- 

 paratively small quantity of any steam or vapor. If 

 a gallon of water is converted into steam, the steam 

 formed will not be sensibly any hotter than boiling 

 water, yet it contains so much latent heat that, if it is 



