ve observed that a large bubble, or a succession
of them has risen from the bottom to the surface. Now, of what gas was
that bubble composed?"

The unhappy student, with the one idea always fermenting on his brain,
felt that the worst had come upon him. Without a moment's hesitation or
thought he expressed his conviction that the compound was cacodyl.

Never did two men look more surprised, and never did two generally grave
_savants_ laugh more heartily than did the two examiners when they
realized what the candidate had answered. Their mirth speedily brought
him back to his senses. He saw with a feeling of despair that it was
marsh gas which they had expected--one of the simplest and commonest of
chemical combinations. Alas! it was too late now. He knew full well
that nothing could save him. With poor marks in botany and zoology,
such an error in chemistry was irreparable. He did what was perhaps the
best thing under the circumstances. Rising from his chair he made a
respectful bow to the examiners, and walked straight out of the room--to
the great astonishment of the janitor, who had never before witnessed
such a breach of decorum. As the student closed the door behind him he
looked back and saw that the other professors had left their respective
tables and were listening to an account of the incident from one of the
chemists--and a roar of laughter the moment afterwards showed that they
appreciated the humour of it. His fellow-students gathered round Tom
outside in the hope of sharing in the joke, but he pushed them angrily
aside and strode through the midst of them and down the University
steps. He knew that the story would spread fast enough without his
assistance. His mind was busy too in shaping a certain resolution which
he had often thought over during the last few months.

The two old people and Miss Kate Harston waited long and anxiously in
their sitting-room at the hotel for some news of the absentee. The
doctor had, at first, attempted a lofty cynicism and general assumption
of indifference, which rapidly broke down as the time went by, until at
last he was wandering round the room, drumming upon the furniture with
his fingers and showing every other sign of acute impatience.
The window was on the first floor, and Kate had been stationed there as
a sentinel to watch the passing crowd and signal the first sign of
tidings.

"Can't you see him yet?" the doctor asked for the twentieth time.