in the same instant, and
Mr. Garwood was hurled over on his side. The queer part of it
was that the explosion didn't do any real damage to the bench,
though there wasn't a piece of the glass mortar left that was
big enough to see."

"The explosion all went upward. It didn't work sideways or downward?"
asked Chief Coy.

"That's the way we saw it," Dick replied. "And it didn't hurt
either you or Darrin?"

"Not beyond the big scare, and the shock to our ear-drums."

"I wonder what the explosive could have been?" mused the chief
aloud.

"I don't know what was in the mortar in the first place, sir,"
Dick Prescott went on. "All Amos Garwood put in the mortar after
we got there was some chlorate of potash. Then he put the pestle
in and began to grind."

"And then the explosion happened?" followed up Chief Coy.

"Chlorate of potash, eh?" broke in a local druggist, who had halted
and was listening. "Hm! If Garwood ground that stuff with a
pestle, then it doesn't much matter what else was in the mortar!"

"Is the chlorate explosive, sir?" questioned Dick.

"Is it?" mimicked the druggist. "When I first started in to learn
the drug business it was a favorite trick to give an apprentice
one or two small crystals of chlorate to grind in a mortar. After
a lot of accidents, and after a few drug clerks had been send
to jail for playing the trick it became played out in drug stores."

"But I've seen powdered chlorate of potash," interposed Tom Reade,
who was always in search of information.

"Yes," admitted the druggist. "I can show you, at my store, about
ten pounds of the powdered chlorate."

"Then how do they get it into a powder, sir?" pressed Tom. "Do
the manufacturers grind it between big millstones?"

"If any ever did," laughed the druggist, "they never remained
on earth long enough to tell about it. A few pounds of the chlorate,
crushed between millstones, would blow the roof off of the largest
mill you ever saw!"

"But what makes the stuff so explosive?" queried Prescott.

"I don't know whether I can make you understand it," the druggist
replied. "Potassium chlorate is extremely 'rich' in oxygen, and
it is held very loosely in combination. When a piece of the chlorate
is struck a hard blow it sets the oxygen free, and the gas expands
so rapidly that the explosion follows."

On the outskirts of the little crowd stood a new-comer, Ted Teall,
who was drinking in every word that the druggist uttered. Dick
saw