kind of acid, and that the sugar was a combination of carbonic acid and
some base to form the alcohol, and that the yeast combined with this
substance, and set free the carbonic acid; just as when you add
carbonate of soda to acid you turn out the carbonic acid. But of course
the discovery of Lavoisier that the carbonic acid and the alcohol taken
together are very nearly equal in weight to the sugar, completely upset
this hypothesis. Another view was therefore taken by the French
chemist, Thenard, and it is still held by a very eminent chemist, M.
Pasteur, and their view is this, that the yeast, so to speak, eats a
little of the sugar, turns a little of it to its own purposes, and by
so doing gives such a shape to the sugar that the rest of it breaks up
into carbonic acid and alcohol.

Well, then, there is a third hypothesis, which is maintained by another
very distinguished chemist, Liebig, which denies either of the other
two, and which declares that the particles of the sugar are, as it
were, shaken asunder by the forces at work in the yeast plant. Now I
am not going to take you into these refinements of chemical theory, I
cannot for a moment pretend to do so, but I may put the case before you
by an analogy. Suppose you compare the sugar to a card house, and
suppose you compare the yeast to a child coming near the card house,
then Fabroni's hypothesis was that the child took half the cards away;
Thenard's and Pasteur's hypothesis is that the child pulls out the
bottom card and thus makes it tumble to pieces; and Liebig's hypothesis
is that the child comes by and shakes the table and tumbles the house
down. I appeal to my friend here (Professor Roscoe) whether that is not
a fair statement of the case.

Having thus, as far as I can, discussed the general state of the
question, it remains only that I should speak of some of those