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'hich  is yielded when coal burns can be measur 
ument by finding out how warm it can make 
old water. The amount of heat which is needed t 
s-uarters of water one degree hotter is called a Ca] 
e changed  into other forms of energy.  When th 
rial force of the coal, which was chemical force, 
eat, then used to convert water into steam, and, lastl: 
lifting the lid. The same coal in a suitable engine 
[mst any kind of work, and the amount of work 
Bckoned in calories. 
coal is burnt on the fire so food is burnt in 6ur bodie 
lowly, of course, and there is no severe heat, but ti 
ig oi  in each case, with the same result, warmth.I 
Luces power for all our actions, aTid the amount of  p 
* deed    upon the energy or fuel value which on 
lue of our food can be measured in calories by the an 
LBsurely as the weight of food can be measured in p 
r of calories (or food units) in a pound of food tell. 
rishment it contains. 
energy value, caloric value, and food value all m 
value ..           ..          .  *   .. 
y circumstances, the greater part of our food goes 
'e-quarters of it or more. Most of the rest is used fo 
uscle and the breathing muscles are always movii 
se a great deal of food; it is when har work such ai 
or diggn fooghours is done that the muscles need 
Ter.  Energy is also needed, though uh   less, I 
iges which go on in the body, such as the digestion o: 
understood