Mater an& 1fce, WQ 



tential (possible) energy, and has the power to 

 do work if released. Active energy is called 

 kinetic (moving) energy, and the sum of these 

 two energies is a constant quantity. 



We will now study energy as it is related to 

 water in the form of heat. There is a kind 

 of heat called " latent heat," which is not heat 

 at all, but stored energy, waiting to be turned 

 into heat, or light, or some other active form. 

 Properly speaking, heat is a movement of the 

 atoms of matter, the intensity of which is 

 measurable in degrees, and called its tempera- 

 ture. To use the term latent heat as meaning 

 concealed heat, which must reappear as heat, 

 is a misnomer and is very misleading. If it 

 is proper to call a wound-up spring or weight 

 latent heat then its present use is a correct 

 one. What was formerly termed latent heat 

 is simply a form of potential energy. When 

 sensible heat that is measurable, as tempera- 

 ture, disappears in the performance of some 

 sort of work, especially in connection with cer- 

 tain phenomena relating to water, we call it 

 or rather miscall it latent heat: but the 

 phrase would better be " stored energy." 



The action of water under heat is very 

 peculiar, and in order to get a correct under- 

 standing of the phenomena exhibited in 

 glacial action we also need to understand the 

 phenomena of water at the freezing point. 

 As is well known, fresh water freezes at 32 de- 



