A HARD-WORKING DIET. 19 
substance results in the formation of ammonia, then 
if the theory be correct, the heavier the work done the 
more should be the amount of ammonia given off. 
But several trials showed this does not take place. 
The difficulties led to many experiments in many 
lands. 
The correlation of the physical forces, now so 
familiar to everybody, was then but dimly seen—or 
guessed at rather than seen—in the far distance. 
But while many of Liebig’s pupils and followers were 
experimenting on themselves and other people as ta 
the connection between food, work and the amounts 
of carbonic acid and ammonia given off, Joule was 
working out questions connected with the conversion 
of heat into motion and motion into heat. 
At last, in 1866, Frankland, taking the results of 
many experiments, and his own laboratory work, as 
his data, worked out the figures showing the CON- 
NECTION BETWEEN MUSCULAR FORCE AND THE 
OXIDATION OF CARBON AND HYDROGEN, and at a 
lecture at the Royal Institution, made the triumphant 
announcement HERE IS THE SOURCE OF MUSCULAR The source of 
POWER. (For “hard.” work, see p. 28.) see 
Liebig, loving truth more than self-glorification, 
eventually recognised his former mistake, and the 
controversy that existed has passed into oblivion. 
The same rough and ready way of showing that How to ex- 
: alts ; perimentally 
carbonic acid is formed by the oxidation of candle fat recognise the 
(p. 13), will suffice to show that carbonic acid is given ene e: 
off in the breath. It is only requisite to blow through 
a tube into clear lime water to see by the formation 
of carbonate of lime that there is much carbonic acid in 
the air we breathe out. Again, it requires no apparatus 
