sharply to the left
along the North Gallery, from the centre of which we entered the Fourth
Egyptian Room.

Almost immediately, a door in the opposite wall opened; a peculiar,
high-pitched humming sound became audible, and Jervis came out on tiptoe
with his hand raised.

"Tread as lightly as you can," he said. "We are just making an
exposure."

The attendant turned back with his lantern, and we followed Jervis into
the room from whence he had come. It was a large room, and little
lighter than the galleries, for the single glow-lamp that burned at the
end where we entered left the rest of the apartment in almost complete
obscurity. We seated ourselves at once on the chairs that had been
placed for us, and, when the mutual salutations had been exchanged, I
looked about me. There were three people in the room besides Jervis:
Thorndyke, who sat with his watch in his hand, a grey-headed gentleman
whom I took to be Dr. Norbury, and a smaller person at the dim farther
end--undistinguishable, but probably Polton. At our end of the room were
the two large trays that I had seen in the workshop, now mounted on
trestles and each fitted with a rubber drain-tube leading down to a
bucket. At the farther end of the room the sinister shape of the gallows
reared itself aloft in the gloom; only now I could see that it was not a
gallows at all. For affixed to the top cross-bar was a large,
bottomless glass basin, inside which was a glass bulb that glowed with a
strange green light; and in the heart of the bulb a bright spot of red.

It was all clear enough so far. The peculiar sound that filled the air
was the hum of the interrupter; the bulb was, of course, a Crookes tube,
and the red spot inside it, the glowing red-hot disc of the
anti-cathode. Clearly an X-ray photograph was being made; but of what? I
strained my eyes, peering into the gloom at the foot of the gallows, but
though I could make out an elongated object lying on the floor directly
under the bulb, I could not resolve the dimly seen shape into anything
recognisable. Presently, however, Dr. Norbury supplied the clue.

"I am rather surprised," said he, "that you chose so composite an object
as a mummy to begin on. I should have thought that a simpler object,
such as a coffin or a wooden figure, would have been more instructive."

"In some ways it would," replied Thorndyke, "but the variety of
materials that the mummy gives us has its advantages. I hope your father
is not