eep except in
two spots where he found irregularities, they were on the midline of
the rectangular base, and equidistant from the ends and sides. Picking
and scraping he uncovered two familiar looking shapes each as big as
his head.

"Mikah. Get down in this hole and look at these things. Tell me what
you think they are."

Mikah scratched his beard. "They're still covered with this metal, I
can't be sure--"

"I'm not asking you to be sure of anything--just tell me what they
make you think of."

"Why ... big nuts of course. Threaded on the ends of bolts. But they
are so big--"

"They would have to be if they hold the entire metal case on. I think
we are getting very close now to the mystery of how to open the
engine--and this is the time to be careful. I still can't believe it
is as easy as this to crack the secret. I'm going to whittle a wooden
template of the nut, then have a wrench made. While I'm gone you stay
down here and pick all the metal off the bolt and out of the screw
threads. I can put off doing it while we think this thing through, but
sooner or later I'm going to have to take a stab at turning one of
those nuts. And I find it very hard to forget about that mustard gas."

Making the wrench put a small strain on the local technology and all
of the old men who enjoyed the title of Masters of the Still went into
consultation over it. One of them was a fair blacksmith and after a
ritual sacrifice and a round of prayers he shoved a bar of iron into
the charcoal and Jason pumped the bellows until it glowed white hot.
With much hammering and cursing it was laboriously formed into a
sturdy open-end wrench with an offset head to get at the countersunk
nuts. Jason made sure that the opening was slightly undersized, then
took the untempered wrench to the work site and filed the jaws to an
exact fit. After being reheated and quenched in oil he had the tool
that he hoped would do the job.

* * * * *

Edipon must have been keeping track of the work progress because he
was waiting near the engine when Jason returned with the completed
wrench.

"I have been under," he announced, "and have seen the nuts that the
devilish Appsalanoj have concealed within solid metal. Who would have
suspected! It still seems to me impossible that one metal could be
hidden within another, how could that be done?"

[Illustration]

"Easy enough. The base of the assembled engine was put into a form a