e young man's bosom.

"What do you know about cacodyl?" was his impressive question.

"Cacodyl?" Tom cried aghast. "It's some sort of antediluvian reptile,
isn't it?"

The questioner broke into a sickly smile. "No," he said. "It's an
organic explosive chemical compound. You're sure to be asked about
cacodyl. Tester's dead on it. He asks every one how it is prepared."

Tom, much perturbed at these tidings, was feverishly endeavouring to
extract some little information from his companion concerning the
compound, when a bell rang abruptly inside the room and a janitor with a
red face and a blue slip of paper appeared at the door.

"Dillon, Dimsdale, Douglas," this functionary shouted in a very pompous
voice, and three unhappy young men filed through the half-opened door
into the solemn hall beyond.

The scene inside was not calculated to put them at their ease. Three
tables, half a dozen yards from each other, were littered with various
specimens and scientific instruments, and behind each sat two elderly
gentlemen, stern-faced and critical. At one side were stuffed specimens
of various small beasts, numerous skeletons and skulls, large jars
containing fish and reptiles preserved in spirits of wine, jawbones with
great teeth which grinned savagely at the unfortunate candidate, and
numerous other zoological relics. The second table was heaped over with
a blaze of gorgeous orchids and tropical plants, which looked strangely
out of place in the great bleak room. A row of microscopes bristled
along the edge. The third was the most appalling of all, for it was
bare with the exception of several sheets of paper and a pencil.
Chemistry was the most dangerous of the many traps set to ensnare the
unwary student.

"Dillon--botany; Dimsdale--zoology; Douglas--chemistry," the janitor
shouted once more, and the candidates moved in front of the respective
tables. Tom found himself facing a great spider crab, which appeared to
be regarding him with a most malignant expression upon its crustacean
features. Behind the crab sat a little professor, whose projecting eyes
and crooked arms gave him such a resemblance to the creature in front
that the student could not help smiling.

"Sir," said a tall, clean-shaven man at the other end of the table, "be
serious. This is no time for levity."

Tom's expression after that would have made the fortune of a mute.

"What is this?" asked the little professor, handing a small r