XXX. The Fermentation of Cacao 
more favourably with petrol than is popularly 
supposed. The fuel consumption of internal 
combustion engines using alcohol is from 370 
to 380 grm., or about 13 oz. to 13°5 oz. per 
effective horse-power hour; and when using 
alcohol of a calorific value of 6,000 calories 
there is obtained a thermal efficiency of some 
22 per cent. At one time alcohol was in 
commercial use in Berlin for automobile work, 
but by reason of its high price, compared with 
that of petrol, its use was discontinued ; and in 
Paris it has been used successfully with an 
equal proportion of benzol for motor-buses. 
“In internal combustion engines using alcohol 
the explosive mixture can be compressed to 
a much higher degree than can a mixture of 
petrol vapour and air before self-ignition takes 
place. When the alcohol is hydrated, the 
compression can be carried still further, so that, 
although the fuel is poorer, a larger percentage 
of it can be converted into useful work. In 
practice the compression is carried to 10 or 14 
atmospheres, this high figure being made 
possible by the water which is present in the 
alcohol used. It is a ‘fact that alcohol when 
slightly adulterated with water is a better fuel 
than when pure. — 
‘‘As to the properties of alcohol, from experi- 
ments the heat value of alcohol appears to lie 
between 13,310 and 11,664 B.t.u. per Ib., ‘the 
latter value being the one most generally 
accepted. One gallon of pure alcohol (specific 
