FERMENTATION. 89 



grape sugar, consisting of three kinds of blocks, six of car- 

 bon, twelve of hydrogen, and six of oxygen, all built into a 

 high tower of twenty-four blocks (sugar, C 6 H I3 O 6 ). In the 

 process of fermentation the equilibrium is disturbed, and we 

 have the tall tower replaced by four smaller ones, two con- 

 sisting of three blocks each (2CO 2 , carbonic acid), and two 

 consisting of nine blocks each (2C 2 H 6 O, alcohol), and the 

 heat that is evolved in the process may be represented by 

 the sum of the figures representing the distances which these 

 various blocks have had to fall from the high tower into the 

 lower ones, multiplied by the figures representing the mass 

 of the volumes. Other features have to be taken into 

 account, but the above example will serve to explain part of 

 our meaning. But this is not all. The children's line of 

 " soldiers " may be used to explain another feature : a 

 child arranges its wooden "bricks" in a long line, placing 

 them on end ; if they are all of equal length the distances be- 

 tween them are also made equal ; if they are of unequal length, 

 they are so arranged that one block falling will just touch the 

 one next to it. If the end block be now so disturbed that it 

 loses its unstable equilibrium, and so falls as to acquire a 

 stable equilibrium, it not only loses its own unstable equili- 

 brium, but it upsets that of the brick next to it, which in 

 turn acts on its neighbour, and so on till the whole line is 

 brought to the ground. If, instead of upsetting the first brick 

 at once, you simply give it a slight tap and only just move it, 

 instead of falling over, it sways backwards and forwards for a 

 little but then settles into its original position ; you give 

 it another tap, it sways a little further, but still returns to 

 its erect position ; whilst if now you give it a good strong 

 push, or if two of you tap it at the same time, over goes the 

 brick, bringing along with it the whole line to a condition 

 of stable equilibrium. The towers or the rows of erect 

 bricks are fermentable substances, the disturbing forces are 

 those agents that bring about fermentation, and the smaller 

 towers or the bricks laid down in rows instead of on end are 

 the products of fermentation. The larger number of smaller 

 towers contain exactly the same elements as did the smaller 

 number of larger ones. They had energy of position, which 

 is converted into kinetic energy, exactly in proportion to the 

 distance that the elements have to fall ; some of the energy 

 appearing in the form of heat, other parts being used up in 



