tion. To people in the habit of using the lighter mineral oils,
and electricity, this was certainly primitive enough. The difficulty,
however, with the gathering of the nuts was this: Unless gathered at a
certain time it is almost impossible to express the oil, and if kept for
any length of time, particularly in an unripe state, they would become
very rancid.

George pondered over this for some time, and asked the Professor the
cause of it. In response, he said: "Nature has a very peculiar way of
protecting her products. It is the same with nuts, as it is with
potatoes and fruit. Have you ever noticed how unripe fruit withers, when
taken from the tree, and that potatoes shrivel up when they are dug up
before fully matured?"

"That is the trouble with the whole batch of potatoes we now have."

"Unripe fruit and vegetables have an exterior coating which is porous
and pervious to water when it is unripe. But when it fully ripens this
coating is chemically changed into a thin, impervious coating of a
cork-like structure, through which water cannot pass, and as a result
potatoes, and fruit, will keep through an entire winter and become
mellower and better as time goes on."

The colony was dependent for its supply of eggs on the numerous flocks
of prairie chickens which were found in the abounding fields of grain,
particularly barley. It was no trick to bag a half dozen of these birds
at a shot, on account of their numbers, and, as before related, while
Angel never ate any of them, he was the most persistent gatherer because
the beautiful oval eggs attracted him, and George's cakes always
appealed to his fancy.

The difficulty with Angel was he did not discriminate between the good
and the bad eggs, and George was desirous of knowing how to distinguish
between the fresh and spoilt ones.

As usual, the Professor was appealed to and he gave a standard rule for
determining this: "As Angel brings in the eggs put them in a pail of
water, and select only those which fall to the bottom and rest on the
side. An egg several weeks old will remain at the bottom, but the large
end will be much higher than the small end. If it is several months old
the large end will be uppermost, with the small end pointing down; and
if it is thoroughly rotten it will float at the top of the water, with
the pointed side down."

"That is a very curious way of finding it out. I would like to know why
the egg acts in that manner?"

"After an egg i