was developed at the Bureau
and which is being made on an experimental scale for us by the Pyrex
people. It is much stronger than ordinary glass, and is not sensitive to
shock. It is also perfectly transparent to ultra-violet light, being
superior even to rock crystal or fused quartz in that respect. The
walls, as you have noticed, are four inches thick, and I have calculated
that the ball will stand a uniform external pressure of thirty-five
hundred atmospheres, the pressure which would be encountered at a depth
of about twenty miles. I believe that it will stand a squeeze of six
thousand tons without buckling, and it is impossible to fracture it by
shock. It could be dropped from the top of the Woolworth Building, and
it would just bounce."

"It seems incredible that it could stand such a pressure as you have
named."

"My figures are conservative ones. Lambertson calculated them even
higher, but we allowed for the fact that this is the first large mass of
the material to be cast, and lowered them."

* * * * *

"But suppose your lifting cable should break?" objected the naval
officer. "The outfit weighs a good many tons."

"You notice that the lower quarter is made of lead. The specific gravity
of the entire globe when sealed up tight with two men in it is only a
little more than unity. In the water its weight is so little that a
three-inch manilla hawser would raise it, let alone a steel cable. I
have another safety device. Granted that the cable should snap, I can
detach the lead from it and it would shoot to the surface like a
rocket."

"How long can you remain under water in it?"

"A week, if necessary. I have an oxygen tank and a carbon dioxide
removing apparatus which will keep the air in good condition. The globe
is electrically lighted, and can be heated if necessary. Should my
telephone line become fouled and broken, I have a radio set which will
enable me to communicate with you. I can't see that it is especially
dangerous; not nearly as much so as a submarine."

"What is your object in going down, if I may ask?"

"To take pictures and to explore the wreck if we can. The globe is
equipped with huge floodlights and excellent cameras. The salvage people
are having a little trouble and we are trying to help them out."

"You mentioned exploring. Can you leave the globe while it is under
water?"

"Yes. There is a locking device for doing so. A man in a diving suit can