and what is all this? Expecting company?"

"Yes; this is a birthday party."

[Illustration: _"'What is this, a party?' said the professor. 'Yes, a
birthday party,' said Harry"_]

"That is a good idea. I suppose you have invited all your friends?"

"Yes; we have invited all we know; just one."

The Professor did not need to be told any more than this. His eyes
filled with tears, the first real thing that the boys ever saw on his
part that strongly affected them, and when the Professor, his heart so
full that he could not speak, silently looked at them, they forgot the
feast, and the cakes, and Baby. They thought of home and of what they
were doing there, and whether the time would ever come when they might
be rescued.

Brave Harry was the first to recover. Like a veteran he grasped the
Professor by the hand, and wished him many a happy return of the day,
and George, though not so demonstrative, joined Harry in this wish and
prayer. Just then one of George's cakes fell at his feet. He picked it
up and Harry glanced at the Baby. The mysterious disappearance had been
solved.

No! Baby was not spanked. He came down without any coaxing, with several
of the cookies in his hand, and gravely took his place at the table.
What a very narrow margin there is between tears and laughter. They
roared as though such a thing as tears were unknown.

When they recovered from their fits of laughter, and attempted to
proceed with the feast in some semblance of order, a glance at Baby was
sufficient to start them up anew. And here a surprising thing occurred.
As before stated, he never had been known to laugh. But now Baby
laughed, for the first time. And then the boys and the Professor knew
that this was also the first time they had indulged in a hearty laugh.

"You may say what you please," said the Professor, "but laughter is
infectious. How much farther a smile will go than a frown. And this
reminds me of a very curious thing in nature. What are called perfumes
have been known to carry through the air for ten miles. The odor from
the balsam-yielding Humeriads has been perceived at a distance of four
miles from the shores of South America; a species of Tetracera sends its
perfume as far as that from Cuba, and the aroma of the Spice Islands is
wafted many miles to sea. Now the singular thing is, that vile and
injurious odors are not carried such distances."

"Why not?"

"For the reason that the oxygen of the air destroys the ba